Systems and methods for air vehicles

ABSTRACT

A refueling device for use in in-flight refueling operation between a tanker aircraft and a receiver aircraft includes a selectively steerable body and a controller. The selectively steerable body configured for being towed by a tanker aircraft via a fuel hose at least during in-flight refueling, and includes a boom member having a boom axis and configured to enable fuel to be transferred from the fuel hose to a receiver aircraft along the boom axis during the in-flight refueling operation. The controller is configured for selectively steering the body to an engagement enabling position spaced with respect to the receiver aircraft and for aligning the boom axis in an engagement enabling orientation at the spaced position, and for subsequently moving the boom member along the boom axis towards the receiver aircraft for enabling fuel communication therebetween.

TECHNOLOGICAL FIELD

The presently disclosed subject matter relates to systems and methodsfor refueling air vehicles, especially aircraft, in particular forrefueling aircraft during flight.

BACKGROUND

Airborne refueling (also referred to interchangeably herein as airrefueling, in-flight refueling, air to air refueling (AAR), aerialrefueling, tanking, and the like) refers to the process of transferringfuel from a tanker aircraft to a receiver aircraft during flight.

Two types of airborne refueling systems are currently in use forrefueling airborne military aircraft:

-   -   the so-called “hose and drogue” system, used by the US Navy and        many non-US air forces;    -   the so-called “boom and receptacle” or “flying boom” system,        used by the US Air Force, and also used by Israel, Turkey and        the Netherlands.

In the hose and drogue system, the refueling aircraft is provided withone or more non-rigid refueling lines, at the end of each of which thereis a drogue which functions as a stabilizer and includes a receptacle,while the receiver aircraft is fitted with a probe that is configuredfor engaging with the receptacle. In use, the drogue is not activelycontrolled, but rather aligns itself freely in the airflow aft of thetanker. The pilot of the receiver aircraft controls the flight paththereof to ensure engaging contact between the probe and the receptacle.Thereafter, the receiver aircraft is refueled via the refueling line andprobe.

In the boom and receptacle system, the tanker includes a so-called“flying boom”, which is a rigid tube that telescopes outwardly and isgimbaled to the rear of the tanker aircraft, and is otherwise retractedinto the tanker fuselage when not in use. The boom carries a fuel lineand comprises a fuel transfer nozzle at the end thereof, and the boom isequipped with adjustable flight control surfaces. Once the tanker andreceiver aircraft are in close proximity and flying in formation, withthe receiver aircraft at a position behind the tanker within an airrefueling envelope (i.e., safe limits of travel for the boom withrespect to the receiver aircraft and within which contact between thereceiving aircraft and the boom is safe), a dedicated operator in thetanker controls the position of the boom via the control surfaces, andinserts the end of the boom including the nozzle into a receptacleprovided on an upper part of the receiving aircraft, ensuring propermating between the nozzle and receptacle, after which fuel transfer canbegin. During refueling, and while the boom is engaged with thereceptacle, the pilot of the receiver aircraft must continue to flywithin the air refueling envelope, and if the receiver aircraftapproaches these limits the operator in the tanker requires the receiveraircraft pilot to correct the position thereof, and if necessary theboom is disconnected to prevent accidents. All current tankers of thistype carry a single boom and can refuel a single receiver aircraft ofthis type at a time.

In addition, there are some tankers that comprise a flying boom systemand at least one hose and drogue system as well, and are commonly knownas Multi-Point Refueling Systems (MPRS). In some cases a hose and droguesystem is provided at the aircraft tail, and thus only this system orthe flying boom system may be used at any one time. In other cases, twounder-wing hose and drogue pods, known as Wing Air Refueling Pods(WARPs), can be provided, one under each wing, in addition to the flyingboom system.

U.S. Pat. No. 7,562,847 discloses an autonomous in-flight refueling hoseend unit including a first end configured to be coupled to a fuel hoseof a tanker aircraft and a second end configured to be coupled toreceiver aircraft and adjustable control surfaces, and a flight controlcomputer autonomously controls the control surfaces to fly the refuelinghose end into contact with the receiver aircraft.

In GB 2,237,251 an in flight refueling apparatus mountable on a tankeraircraft has a probe receptor coupled with a fuel line and is arrangedto be deployed outboard of the aircraft, and can be provided on a drogueor a boom. In one mode, the apparatus is arranged to provide a parameterwhich is representative of the deviation of the path of the receptorfrom a predetermined initial path for actuating control means forchanging automatically the position of the receptor relative to theinitial path. In another mode, a parameter which is representative ofthe relative angular position of the receptor with respect to the probeof an approaching refueling aircraft for actuating control means forchanging automatically the relative angular position to achievealignment of receptor and probe.

By way of general background, the following publications disclosein-flight refueling systems or components thereof: US 2007/108339, US2007/084968, US 2006/065785, US 2006/043241, US 2006/060710, US2006/060709, US 2005/224657, US 2004/102876, U.S. Pat. Nos. 7,097,139,6,966,525, 6,994,294, 6,644,594, 5,906,336, 5,785,276, 5,499,784,5,326,052, 4,282,909, 4,126,162, 4,072,283, 3,948,626, 3,091,419,3,059,895, 2,954,190, 2,582,609, D 439,876, DE 100 13 751.

GENERAL DESCRIPTION

In accordance with an aspect of the presently disclosed subject matter,there is provided a method for controlling in-flight refueling of areceiver aircraft having a fuel receptacle, comprising automaticallysteering a refueling device to an engagement enabling position,including:

-   -   (i) repeatedly determining a spatial disposition of the        refueling device with respect to the receiver aircraft, the        refueling device being capable of engaging and refueling the        receiver aircraft via a boom member, when the device arrives to        the engagement enabling position at which the boom member is in        a predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculating steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) sending the steering commands to the spatial control        system;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is further provided a method, comprising providing aninstruction to the refueling device, in response to its arriving at theengagement enabling position, causing the refueling device to move theboom member in a predetermined trajectory for automatically engagingwith the fuel receptacle.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the boom memberhas a boom axis and wherein at least a final part of the predeterminedtrajectory is parallel to the boom axis.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, further comprisingdetermining an engagement area specification condition; repeatedlycalculating maneuvering instructions for the receiver aircraft based onthe spatial dispositions and an engagement area specification; andinvoking the automatic steering in response to meeting the engagementarea specification condition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the refuelingdevice is connected to a tanker aircraft by a fuel hose, and furthercomprising providing the maneuvering instructions to at least one of apilot of the receiver aircraft pilot or a pilot of the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein providing themaneuvering instructions comprises activating a signaling system,optionally mounted on the refueling device or the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, further comprisingactivating a force generating arrangement in the refueling device forgenerating force in the direction of the fuel receptacle of the receiveraircraft in response to receiving an engagement command for enablingrefueling.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the determininga spatial disposition comprises acquiring an image of said receiveraircraft, comparing the image with a reference image depicting a desiredspatial disposition of the refueling device with respect to a receiveraircraft, and determining, based on the comparing, the spatialdisposition of the refueling device with respect to the receiveraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the spatialcontrol system characteristics are related to operation parameters ofaero-dynamic control surfaces of the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the aero-dynamiccontrol surfaces are one or more vanes.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the spatialcontrol system characteristics are related to operation parameters ofreaction control thrusters associated with the refueling device andcapable of steering the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the engagementarea specification condition is a spatial disposition within apre-determined volume with respect to the refueling device and whereinthe pre-determined volume is optionally substantially in the shape of acube or substantially in the shape of a sphere.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the calculatingsteering commands comprises obtaining data of an initial trail positionof the refueling device and wherein the steering commands are based alsoon the data of an initial trail position.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the data of aninitial trail position includes at least one of a pitch angle of therefueling device, a yaw angle of the refueling device, and a deploymentlength of a fuel hose connecting the refueling device to the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the automaticsteering and the automatic engaging are performed autonomously by therefueling device.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) automatically steering a refueling device to an engagement        enabling position, including:        -   (i) repeatedly determining a spatial disposition of the            refueling device with respect to the receiver aircraft, the            refueling device being capable of engaging and refueling the            receiver aircraft via a boom member, when the device arrives            to the engagement enabling position at which the boom member            is in a predetermined spaced and spatial relationship with            respect to the fuel receptacle of the receiver aircraft;        -   (ii) repeatedly calculating steering commands based at least            on the repeatedly determined spatial dispositions and            characteristics of a spatial control system of the refueling            device;        -   (iii) sending the steering commands to the spatial control            system;    -   (b) providing an instruction to the refueling device, when it        arrives at the engagement enabling position, for causing the        refueling device to move the boom member along a predetermined        trajectory for automatically engaging with the fuel receptacle.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the boom memberhas a boom axis and wherein at least a final part of the predeterminedtrajectory is parallel to the boom axis.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, further comprisinginvoking the automatic steering in response to a spatial dispositionbetween the refueling device and the receiver aircraft meeting anengagement area specification condition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, further comprisingrepeatedly calculating maneuvering instructions for the receiveraircraft based on spatial dispositions and an engagement areaspecification, for establishing the spatial disposition between therefueling device and the receiver aircraft that meets the engagementarea specification condition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the refuelingdevice is connected to a tanker aircraft by a fuel hose, and furthercomprising providing the maneuvering instructions to at least one of apilot of the receiver aircraft or a pilot of the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein providing themaneuvering instructions comprises activating a signaling system,optionally mounted on the refueling device or the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method further comprisingactivating a force generating arrangement in the refueling device forgenerating force in the direction of the fuel receptacle of the receiveraircraft in response to receiving an engagement command for enablingrefueling.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the determininga spatial disposition comprises acquiring an image of the receiveraircraft, comparing the image with a reference image depicting a desiredspatial disposition of the refueling device with respect to a receiveraircraft, determining, based on the comparing, the spatial dispositionof the refueling device with respect to the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the spatialcontrol system characteristics are related to operation parameters ofaero-dynamic control surfaces of the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the aero-dynamiccontrol surfaces are one or more vanes.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the spatialcontrol system characteristics are related to operation parameters ofreaction control thrusters associated with the refueling device and,capable of steering the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the engagementarea specification condition is a spatial disposition within apre-determined volume with respect to the refueling device and whereinthe pre-determined volume is optionally substantially in the shape of acube or substantially in the shape of a sphere.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the calculatingsteering commands comprises obtaining data of an initial trail positionof the refueling device and wherein the steering commands are based alsoon the data of an initial trail position.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the data of aninitial trail position includes at least one of a pitch angle of therefueling device, a yaw angle of the refueling device, and a deploymentlength of a fuel hose connecting the refueling device to the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the automaticsteering and the automatic engaging are performed autonomously by therefueling device.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) repeatedly calculating maneuvering instructions for the        receiver aircraft based on spatial dispositions of the receiver        aircraft and an engagement area specification until an        engagement area specification condition is met;    -   (b) in response to meeting the engagement area specification        condition, automatically steering a refueling device to an        engagement enabling position, including:        -   (i) repeatedly determining a spatial disposition of the            refueling device with respect to the receiver aircraft, the            refueling device being capable of engaging and refueling the            receiver aircraft via a boom member, when the refueling            device arrives to the engagement enabling position at which            the boom member is in a predetermined spaced and spatial            relationship with respect to the fuel receptacle of the            receiver aircraft;        -   (ii) repeatedly calculating steering commands based at least            on the repeatedly determined spatial dispositions and            characteristics of a spatial control system of the refueling            device;        -   (iii) sending the steering commands to the spatial control            system;    -   (c) providing an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory for automatically engaging with the        fuel receptacle.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method wherein the boom memberhas a boom axis and wherein at least a final part of the predeterminedtrajectory is parallel to the boom axis.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the refuelingdevice is connected to a tanker aircraft by a fuel hose, and furthercomprising providing the maneuvering instructions to at least one of apilot of the receiver aircraft or a pilot of the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein providing themaneuvering instructions comprises activating a signaling system,optionally mounted on the refueling device or the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method further comprisingactivating a force generating arrangement in the refueling device forgenerating force in the direction of the fuel receptacle of the receiveraircraft in response to receiving an engagement command for enablingrefueling.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the determininga spatial disposition comprises acquiring an image of the receiveraircraft; comparing the image with a reference image depicting a desiredspatial disposition of the refueling device with respect to a receiveraircraft; and determining, based on the comparing, the spatialdisposition of the refueling device with respect to the receiveraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the spatialcontrol system characteristics are related to operation parameters ofaero-dynamic control surfaces of the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the aero-dynamiccontrol surfaces are one or more vanes.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the spatialcontrol system characteristics are related to operation parameters ofreaction control thrusters associated with the refueling device andcapable of steering the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the engagementarea specification condition is a spatial disposition within apre-determined volume with respect to the refueling device and whereinthe pre-determined volume is optionally substantially in the shape of acube or substantially in the shape of a sphere.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the calculatingsteering commands comprises obtaining data of an initial trail positionof the refueling device and wherein the steering commands are based alsoon the data of an initial trail position.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the data of aninitial trail position includes at least one of a pitch angle of therefueling device, a yaw angle of the refueling device, and a deploymentlength of a fuel hose connecting the refueling device to the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a method, wherein the automaticsteering and the automatic engaging are performed autonomously by therefueling device.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising asteering control module configured to automatically steer a refuelingdevice to an engagement enabling position, including:

-   -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the steering commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, further comprising anengagement/disengagement module configured to provide an instruction tothe refueling device, in response to its arriving at the engagementenabling position, causing the refueling device to move the boom memberin a predetermined trajectory to automatically engage with the fuelreceptacle.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the boom memberhas a boom axis and wherein at least a final part of the predeterminedtrajectory is parallel to the boom axis.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, further comprising amaneuvering instructions module configured to determine an engagementarea specification condition, to repeatedly calculate maneuveringinstructions for the receiver aircraft based on the spatial dispositionsand an engagement area specification, and to invoke the steering controlmodule to automatically steer the refueling device to the engagementenabling position in response to meeting the engagement areaspecification condition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the refuelingdevice is connected to a tanker aircraft by a fuel hose, and wherein themaneuvering instructions module is further configured to provide themaneuvering instructions to at least one of a pilot of the receiveraircraft pilot or a pilot of the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the maneuveringinstructions module is configured to activate a signaling system inorder to provide the maneuvering instructions, the signaling system isoptionally mounted on the refueling device or the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein theengagement/disengagement module is further configured to activate aforce generating arrangement in the refueling device for generatingforce in the direction of the fuel receptacle of the receiver aircraftin response to receiving an engagement command for enabling refueling.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the steeringcontrol module is configured to perform the following steps in order todetermine a spatial disposition: acquire an image of the receiveraircraft; compare the image with a reference image depicting a desiredspatial disposition of the refueling device with respect to a receiveraircraft; determine, based on the comparing, the spatial disposition ofthe refueling device with respect to the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the spatialcontrol system characteristics are related to operation parameters ofaero-dynamic control surfaces of the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the aero-dynamiccontrol surfaces are one or more vanes.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the spatialcontrol system characteristics are related to operation parameters ofreaction control thrusters associated with the refueling device andcapable of steering the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the engagementarea specification condition is a spatial disposition within apre-determined volume with respect to the refueling device and whereinthe pre-determined volume is optionally substantially in the shape of acube or substantially in the shape of a sphere.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the steeringcontrol module is further configured to obtain data of an initial trailposition of the refueling device and wherein the calculate steeringcommands is based also on the obtained data of an initial trailposition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the data of aninitial trail position includes at least one of a pitch angle of therefueling device, a yaw angle of the refueling device, and a deploymentlength of a fuel hose connecting the refueling device to the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the refueling device for enabling autonomously controllingin-flight refueling of the receiver aircraft by the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the tanker aircraft.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising asteering control module configured to automatically steer a refuelingdevice to an engagement enabling position, including:

-   -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the steering commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device,        when it arrives at the engagement enabling position, for causing        the refueling device to move the boom member along a        predetermined trajectory to automatically engage with the fuel        receptacle.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the boom memberhas a boom axis and wherein at least a final part of the predeterminedtrajectory is parallel to the boom axis.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, further comprising amaneuvering instructions module configured to invoke the steeringcontrol module to automatically steer the refueling device to theengagement enabling position in response to meeting an engagement areaspecification condition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system wherein the maneuveringinstructions module is further configured to repeatedly calculatemaneuvering instructions for the receiver aircraft based on spatialdispositions and an engagement area specification, for establishing thespatial disposition between the refueling device and the receiveraircraft that meets the engagement area specification condition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the refuelingdevice is connected to a tanker aircraft by a fuel hose, and wherein themaneuvering instructions module is further configured to provide themaneuvering instructions to at least one of a pilot of the receiveraircraft or a pilot of the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the maneuveringinstructions module is configured to activate a signaling system inorder to provide the maneuvering instructions, and wherein the signalingsystem is optionally mounted on the refueling device or the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system wherein theengagement/disengagement module is further configured to activate aforce generating arrangement in the refueling device for generatingforce in the direction of the fuel receptacle of the receiver aircraftin response to receiving an engagement command for enabling refueling.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein determining aspatial disposition comprises:

-   -   acquire an image of the receiver aircraft;    -   compare the image with a reference image depicting a desired        spatial disposition of the refueling device with respect to a        receiver aircraft;    -   determine, based on the comparison, the spatial disposition of        the refueling device with respect to the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the spatialcontrol system characteristics are related to operation parameters ofaero-dynamic control surfaces of the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the aero-dynamiccontrol surfaces are one or more vanes.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the spatialcontrol system characteristics are related to operation parameters ofreaction control thrusters associated with the refueling device andcapable of steering the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the engagementarea specification condition is a spatial disposition within apre-determined volume with respect to the refueling device and whereinthe pre-determined volume is optionally substantially in the shape of acube or substantially in the shape of a sphere.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the steeringcontrol module is further configured to obtain data of an initial trailposition of the refueling device and wherein the calculate steeringcommands is based also on the obtained data of an initial trailposition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the data of aninitial trail position includes at least one of a pitch angle of therefueling device, a yaw angle of the refueling device, and a deploymentlength of a fuel hose connecting the refueling device to the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the refueling device for enabling autonomously controllingin-flight refueling of the receiver aircraft by the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the tanker aircraft.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising amaneuvering instructions module configured to repeatedly calculatemaneuvering instructions for the receiver aircraft based on spatialdispositions of the receiver aircraft and an engagement areaspecification until an engagement area specification condition is met,and in response to meeting the engagement area specification condition,activate a steering control module; the steering control module isconfigured to automatically steer a refueling device to an engagementenabling position, including:

-   -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the steering commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory to automatically engage with the fuel        receptacle.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system wherein the boom memberhas a boom axis and wherein at least a final part of the predeterminedtrajectory is parallel to the boom axis.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the refuelingdevice is connected to a tanker aircraft by a fuel hose, and wherein themaneuvering instructions module is further configured to provide themaneuvering instructions to at least one of a pilot of the receiveraircraft or a pilot of the tanker aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the maneuveringinstructions module is configured to activate a signaling system inorder to provide the maneuvering instructions, and wherein the signalingsystem is optionally mounted on the refueling device or the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system wherein theengagement/disengagement module is further configured to activate aforce generating arrangement in the refueling device for generatingforce in the direction of the fuel receptacle of the receiver aircraftin response to receiving an engagement command for enabling refueling.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the determine aspatial disposition comprises acquire an image of said receiveraircraft; compare the image with a reference image depicting a desiredspatial disposition of the refueling device with respect to a receiveraircraft; determine, based on the comparison, the spatial disposition ofthe refueling device with respect to the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the spatialcontrol system characteristics are related to operation parameters ofaero-dynamic control surfaces of the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the aero-dynamiccontrol surfaces are one or more vanes.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the spatialcontrol system characteristics are related to operation parameters ofreaction control thrusters associated with the refueling device andcapable of steering the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the engagementarea specification condition is a spatial disposition within apre-determined volume with respect to the refueling device and whereinthe pre-determined volume is optionally substantially in the shape of acube or substantially in the shape of a sphere.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the steeringcontrol module is further configured to obtain data of an initial trailposition of the refueling device and wherein the calculate steeringcommands is based also on the obtained data of an initial trailposition.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein the data of aninitial trail position includes at least one of a pitch angle of therefueling device, a yaw angle of the refueling device, and a deploymentlength of a fuel hose connecting the refueling device to the tankeraircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the refueling device for enabling autonomously controllingin-flight refueling of the receiver aircraft by the refueling device.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the receiver aircraft.

In accordance with certain examples of the presently disclosed subjectmatter, there is yet further provided a system, wherein at least thesteering control module and the engagement/disengagement module arefitted within the tanker aircraft.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a refueling device for use in in-flightrefueling operation between a tanker aircraft and a receiver aircraft,comprising a selectively steerable body configured for being towed by atanker aircraft via a fuel hose at least during in-flight refueling, andcomprising a boom member having a boom axis and configured to enablefuel to be transferred from the fuel hose to a receiver aircraft alongthe boom axis during the in-flight refueling operation; a controllerconfigured for selectively steering the body to an engagement enablingposition spaced with respect to the receiver aircraft and for aligningthe boom axis in an engagement enabling orientation at the spacedposition, and for subsequently moving the boom member along the boomaxis towards the receiver aircraft for enabling fuel communicationtherebetween.

According to at least one aspect of the presently disclosed subjectmatter, there is provided a refueling device for use in in-flightrefueling operation between a tanker aircraft and a receiver aircraft,comprising:

-   -   a selectively steerable body configured for being towed by a        tanker aircraft via a fuel hose at least during in-flight        refueling, and comprising a boom member having a boom axis and        configured to enable fuel to be transferred from said fuel hose        to a receiver aircraft along said boom axis during said        in-flight refueling operation;    -   a controller configured for selectively steering the body to an        engagement enabling position spaced with respect to the receiver        aircraft and for aligning said boom axis in an engagement        enabling orientation at said spaced position, and for        subsequently moving the boom member along said boom axis towards        the receiver aircraft for enabling fuel communication        therebetween.

For example, moving the boom member along said boom axis towards thereceiver aircraft for enabling fuel communication therebetween can beachieved by any one of the following, for example:

-   -   by moving the body towards the fuel receptacle of the receiver        aircraft along the direction of the boom axis,    -   by telescopically extending the boom member towards the towards        the fuel receptacle of the receiver aircraft along said boom        axis while the body is maintained at the engagement enabling        position,    -   partially by moving the body towards the fuel receptacle of the        receiver aircraft along the direction of the boom axis, and        partially by telescopically extending the boom member towards        the towards the fuel receptacle of the receiver aircraft along        said boom axis while the body is maintained at the engagement        enabling position.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise a spatial control systemconfigured for selectively ensuring maintaining a desired non-zeroangular disposition between said boom axis and said forward direction atleast when said refueling device is towed by the tanker aircraft in saidforward direction via said fuel hose.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise one or more of features (A) to (S) below,additionally or alternatively including one or more of features (k1) to(k10) below, additionally or alternatively including one or more offeatures (m1) to (m4) below, additionally or alternatively including oneor more of features (n1) to (n4) below, additionally or alternativelyincluding one or more of features (q1) to (q6) below, mutatis mutandis,in any desired combination or permutation.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise a force generating arrangement configuredfor selectively generating a force along said boom axis in a directiongenerally away from said fuel hose, i.e., towards the fuel delivery endof the boom member. Additionally or alternatively to the above features,the refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of features (AA) to(LL) below, mutatis mutandis, in any desired combination or permutation.

Additionally or alternatively to the above features, the body accordingto this aspect of the presently disclosed subject matter can optionallycomprise a fuel delivery lumen configured for fluid communication withsaid fuel hose at least during the in-flight refueling operation, saidlumen being configured to enable fuel to be transferred from the fuelhose to a receiver aircraft during said in-flight refueling operation,and the fuel delivery device comprises a coupling having a hoseinterface configured for connecting said lumen to the fuel hose, saidcoupling configured for allowing relative rotation between the hose andsaid body in at least one degree of freedom while maintaining said fuelcommunication. Additionally or alternatively to the above features, therefueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of features (AAA) to(LLL) below, mutatis mutandis, in any desired combination orpermutation.

According to at least one aspect of the presently disclosed subjectmatter, the refueling device comprises:

-   -   a) a body configured for being towed by a tanker aircraft via a        fuel hose at least during in-flight refueling operation, and        comprising a boom member having a boom axis and configured to        enable fuel to be transferred from said fuel hose to a receiver        aircraft along said axis during said in-flight refueling        operation;    -   (b) spatial control system configured for selectively ensuring        maintaining a desired non-zero angular disposition between said        boom axis and a forward direction at least when said refueling        device is towed by the tanker aircraft in said forward direction        via said fuel hose.

The above refueling device can optionally comprise one or more of thefollowing features, in any desired combination or permutation:

-   -   A. A controller configured for selectively steering the body to        an engagement enabling position spaced with respect to the        receiver aircraft and for aligning said boom axis in an        engagement enabling orientation at said spaced position, and for        subsequently moving the boom member along said boom axis towards        the receiver aircraft for enabling fuel communication        therebetween.    -   B. The boom member comprises a nozzle at a terminus thereof in        fluid communication with a fuel delivery lumen comprised in said        body, said nozzle being configured for reversible engagement        with a fuel receptacle of a receiver aircraft.    -   C. The fuel hose is substantially non-rigid and/or said body is        selectively steerable.    -   D. The desired non-zero angular disposition is selectively        controllable and/or said angular disposition is defined on a        vertical plane.    -   E. The spatial control system configured for at least        maintaining a selectively controllable non-zero angular        disposition between said boom axis and a datum direction        (different from said boom axis); the datum direction can be a        forward direction of the body, i.e., direction of motion of the        body when towed via the hose; the said angular disposition can        be or comprise an angle of attack of said boom axis with respect        to said forward direction.    -   F. The said angular disposition is such as to ensure that the        boom axis is at a predetermined design angle with respect to the        receiver aircraft, in particular with respect to a longitudinal        axis of the receiver aircraft; the design angle is such as to        ensure proper alignment and engagement between the nozzle and        the fuel receptacle; for example, the design angle may be        between about 25° and about 35°, for example about 30°.    -   G. The said angular disposition is defined about a pitch axis of        said refueling device. Additionally or alternatively, said        angular disposition is defined about at least one of a yaw axis        and a roll axis of said refueling device. Additionally or        alternatively, the said angular disposition is in a range        between about 5° and about 85°; preferably between about 10° and        about 80°; more preferably between about 15° and about 70°; more        preferably between about 20° and about 60°; more preferably        between about 25° and about 50°; more preferably between about        20° and about 40°; more preferably between about 25° and about        40°; more preferably between about 28° and about 32°; or said        angular disposition is about 30°.    -   H. Wherein said refueling device is configured for maintaining        said desired non-zero angular disposition between said boom axis        and said forward direction at least prior to engagement of said        nozzle with a fuel receptacle of a receiver aircraft that flying        in formation aft of the tanker aircraft.    -   I. Wherein said spatial control system is further configured for        selectively providing control moments in at least one of pitch,        yaw and roll wherein to enable the refueling device to be flown        while towed by the tanker aircraft in said forward direction via        said fuel hose.    -   J. Wherein said body is elongate having a longitudinal axis        generally aligned with said boom axis.    -   K. Wherein said spatial control system comprises selectively        controllable aerodynamic control system. The selectively        controllable aerodynamic control system can optionally comprise        one or more of the following features, in any desired        combination or permutation:        -   (k1) wherein said selectively controllable aerodynamic            control system comprises a forward set of aerodynamic            control surfaces mounted to said body, and an aft set of            aerodynamic control surfaces mounted to said body in            longitudinally aft spaced relationship with respect to said            forward set of aerodynamic control surfaces.        -   (k2) a center of gravity of said body is disposed in            longitudinally intermediate said forward set of aerodynamic            control surfaces and said aft set of aerodynamic control            surfaces.        -   (k3) wherein said aft set of aerodynamic control surfaces            comprises at least two said control surfaces mounted to said            body in Vee configuration; or wherein said aft set of            aerodynamic control surfaces comprises a high H-tail            configuration, comprising two vertical stabilizers, one each            on either side of a horizontal stabilizer—the H-tail            configuration can be mounted to the upper side of the body,            and optionally: each vertical stabilizer comprises a            controllably pivotable rudder, and/or the horizontal            stabilizer comprises one, two or more pivotable elevators,            which optionally are controllably actuated by an actuator            system for example controlled by a controller.        -   (k4) wherein said aft set of aerodynamic control surfaces            further comprises at least one said control surfaces mounted            to said body in vertical configuration.        -   (k5) wherein said forward set of aerodynamic control            surfaces comprises at least two said control surfaces            mounted to said body in Vee configuration.        -   (k6) wherein said forward set of aerodynamic control            surfaces comprises at least four said control surfaces            mounted to said body in cruciform configuration, for example            cruciform “X” configuration or cruciform “+” configuration.        -   (k7) wherein at least one said control surface is pivotably            mounted to said body via a respective boss laterally            projecting from an outer surface of said body.        -   (k8) wherein each said boss houses an actuator configured            for actuating the respective control surface.        -   (k9) wherein each said boss comprises an aerofoil shaped            cross-sectional shape having a respective chord.        -   (k10) wherein each said chord is angularly displaced from            said boom axis such as to become generally aligned with said            forward direction when said boom axis is at said non-zero            angular disposition with respect to said forward direction.    -   L. Wherein said spatial control system comprises a thrust vector        system.    -   M. A force generating arrangement configured for selectively        generating a force along said boom axis in an aft direction,        i.e., a direction towards said nozzle. The force generating        arrangement can optionally comprise one or more of the following        features, in any desired combination or permutation:        -   (m1) wherein said force generating arrangement comprises a            selectively deployable drag inducing arrangement.        -   (m2) wherein said force generating arrangement comprises a            selectively deployable air brake arrangement.        -   (m3) wherein said air brake arrangement comprises a            plurality of airbrakes laterally mounted to at least one of            said body and said boom member.        -   (m4) wherein said force generating arrangement is configured            for selectively generating said force along said boom axis            in a direction towards said nozzle responsive to said nozzle            being in predetermined proximity to the fuel receptacle of            the receiver aircraft whereby to force said nozzle into            engagement with the fuel receptacle.    -   N. Said body comprises a fuel delivery lumen configured for        fluid communication with said fuel hose and said boom member at        least during the in-flight refueling operation, and said body        comprises a coupling having a hose interface configured for        connecting said lumen to the fuel hose, said coupling configured        for allowing relative rotation between the hose and said body in        at least one degree of freedom while maintaining said fuel        communication. The coupling can optionally comprise one or more        of the following features, in any desired combination or        permutation:        -   (n1) wherein said coupling configured for allowing relative            rotation between the hose and said body in at least two            degrees of freedom.        -   (n2) wherein said coupling configured for allowing relative            rotation between the hose and said body in three degrees of            freedom.        -   (n3) wherein at least one said rotational degree of freedom            has the respective axis of rotation generally orthogonal to            a plane defining said non-zero angular disposition between            said boom axis and said forward direction.        -   (n4) wherein said coupling comprises a universal coupling.    -   O. Wherein said boom member is selectively reversibly        telescopically deployable along said boom axis with respect to        said body.    -   P. Wherein said boom member is pivotably mounted to said body.    -   Q. A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between a fuel        delivery nozzle of the refueling device and a fuel receptacle of        the receiver aircraft, to enable selectively controlling the        refueling device to provide automatic and/or autonomous and/or        manual engagement of the fuel delivery nozzle to the fuel        receptacle of the receiver aircraft. In at least one example,        the system comprises an imaging system for providing said data        including at least image data corresponding to a field of regard        with respect to the refueling device. The data acquisition        system can be in the form of an imaging system, and can        optionally comprise one or more of the following features, in        any desired combination or permutation:        -   (q1) wherein said imaging system is configured for providing            at least one of 2D images, stereoscopic images, and 3D            images of a volume defined by said field of regard.        -   (q2) wherein said imaging system is configured for providing            said image data in real time.        -   (q3) wherein said imaging system comprises or is operatively            connected to a computing system configured for identifying a            fuel receptacle of a receiver aircraft within said field of            regard from said image data, and for determining a spatial            disposition of said nozzle with respect to the fuel            receptacle.        -   (q4) wherein said imaging system comprises a first set of            electromagnetic energy modules configured for illuminating            said field of regard with electromagnetic energy (for            example laser energy), and a second set of electromagnetic            energy modules configured for receiving electromagnetic            energy from said illuminated field of regard.        -   (q5) wherein said imaging system comprises a first set of            electromagnetic energy modules configured for transmitting            electromagnetic energy in a direction generally along said            boom axis and generally opposed to said forward direction,            and a second set of electromagnetic energy modules            configured for receiving electromagnetic energy from a            direction generally along said boom axis and generally along            said forward direction.        -   (q6) wherein said imaging system comprises at least one            flash War unit.    -   R. The controller can comprise, for example, a computer system,        operatively connected to said spatial data acquisition system        and/or to said spatial control system, and/or optionally        configured as an automatic or autonomous system for enabling        refueling device to be steered to an engagement enabling        position to provide engagement of the nozzle with the fuel        receptacle of the receiver aircraft, and thereafter enable        refueling of the receiver aircraft.    -   S. A suitable communication system to transmit image data and to        receive control commands/signals. For example, the        communications system can be operatively connected to the        controller for controlling operation of the refueling device.

According to at least one aspect of the presently disclosed subjectmatter, the refueling device comprises:

-   -   a body configured for connection to a tanker aircraft via a fuel        hose at least during in-flight refueling operation thereof while        said body is in towed configuration with respect to the tanker        aircraft via said fuel hose, and further comprising a        substantially rigid boom member having a boom axis and        configured to enable fuel to be transferred from the tanker        aircraft to a receiver aircraft during said in-flight refueling        operation;    -   spatial control system configured for selectively maintaining a        desired non-zero angular disposition between said boom axis and        a datum direction.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of the followingfeatures, in any desired combination or permutation:

-   -   Wherein said datum direction is parallel to a longitudinal axis        of the receiver aircraft.    -   The desired non-zero angular disposition is selectively        controllable.    -   The datum direction is different, i.e. non-parallel, from said        boom axis.    -   The datum direction can be parallel to a forward direction of        the body, i.e., direction of motion of the body when towed via        the hose.    -   The spatial control system is also configured for selectively        ensuring maintaining a desired non-zero angular disposition        between said boom axis and said forward direction at least when        said refueling device is towed by the tanker aircraft in said        forward direction via said fuel hose.    -   The boom member comprises a nozzle at a terminus thereof in        fluid communication with a fuel delivery lumen comprised in said        body, said nozzle being configured for reversible engagement        with a fuel receptacle of a receiver aircraft.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise one or more of features (A) to (S),additionally or alternatively including one or more of features (k1) to(k10), additionally or alternatively including one or more of features(m1) to (m4), additionally or alternatively including one or more offeatures (n1) to (n4), additionally or alternatively including one ormore of features (q1) to (q6), mutatis mutandis, in any desiredcombination or permutation.

According to at least one other aspect of the presently disclosedsubject matter, the refueling device comprises:

-   -   (aa) a body configured for being towed by a tanker aircraft via        a fuel hose at least during in-flight refueling operation, and        comprising a boom member having a boom axis and configured to        enable fuel to be transferred from said fuel hose to a receiver        aircraft along said axis during said in-flight refueling        operation;    -   (bb) a force generating arrangement configured for selectively        generating a force along said boom axis in a direction generally        away from said fuel hose.

A fuel delivery nozzle is comprised at a terminus of the boom member andis in fluid communication with a fuel delivery lumen comprised in saidbody, the lumen configured for fluid communication with said fuel hoseand said fuel member at least during in flight refueling operation, saidnozzle being configured for reversible engagement with a fuel receptacleof a receiver aircraft.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of the followingfeatures, in any desired combination or permutation:

-   -   (AA) Wherein said force generating arrangement comprises a        selectively deployable drag inducing arrangement.    -   (BB) Wherein said force generating arrangement comprises a        selectively deployable air brake arrangement.    -   (CC) Wherein said air brake arrangement comprises a plurality of        airbrakes laterally mounted to at least one of said body and        said boom member.    -   (DD) Wherein said force generating arrangement is configured for        selectively generating a force along said boom axis in a        direction towards said nozzle responsive to said nozzle being in        predetermined proximity to the fuel receptacle of the receiver        aircraft wherein to force said nozzle into engagement with the        fuel receptacle.    -   (EE) Wherein the fuel hose is substantially non-rigid and/or        wherein said body is selectively steerable.    -   (FF) Wherein said boom member is selectively reversibly        telescopically deployable along said boom axis with respect to        said body.    -   (GG) Wherein said boom member is pivotably mounted to said body.    -   (HH) a controller configured for selectively steering the body        to an engagement enabling position spaced with respect to the        receiver aircraft and for aligning said boom axis in an        engagement enabling orientation at said spaced position, and for        subsequently moving the boom member along said boom axis towards        the receiver aircraft for enabling fuel communication        therebetween.    -   (II). A suitable communication system to transmit image data and        to receive control commands/signals. For example, the        communications system can be operatively connected to the        controller for controlling operation of the refueling device.    -   (JJ) A spatial control system configured for selectively        ensuring maintaining a desired non-zero angular disposition        between said boom axis and said forward direction at least when        said refueling device is towed by the tanker aircraft in said        forward direction via said fuel hose, and/or configured for at        least providing directional stability at least during deployment        of drag generating system, the spatial control system being        different from said force generating arrangement. The spatial        control system according to at least this aspect of the        presently disclosed subject matter can optionally comprise one        or more of features (B) to (L), optionally including one or more        of features (k1) to k(10), mutatis mutandis, in any desired        combination or permutation.    -   (KK) A coupling having a hose interface configured for        connecting said lumen to the fuel hose, said coupling configured        for allowing relative rotation between the hose and said body in        at least one degree of freedom while maintaining said fuel        communication. The coupling according to at least this aspect of        the presently disclosed subject matter can optionally comprise        one or more of features (n1) to (n4), mutatis mutandis, in any        desired combination or permutation.    -   (LL) A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between said        fuel delivery nozzle and a fuel receptacle of the receiver        aircraft, to enable selectively controlling the refueling device        to provide automatic or autonomous or manual engagement of the        fuel delivery end to the fuel receptacle, said system optionally        comprising an imaging system configured for providing said data        including image data corresponding to a field of regard aft of        the refueling device, and wherein optionally said imaging system        comprises or is operatively connected to a computing system        configured for identifying a fuel receptacle of a receiver        aircraft within said field of regard from said image data, and        for determining a spatial disposition of said fuel delivery        nozzle with respect to the fuel receptacle. The data acquisition        system can be in the form of an imaging system, and can        optionally comprise one or more of features (q1) to (q6),        mutatis mutandis, in any desired combination or permutation.

According to at least one other aspect of the presently disclosedsubject matter, the refueling device comprises:

-   -   (aaa) a body configured for being towed by a tanker aircraft via        a fuel hose at least during in-flight refueling operation, and        comprising a fuel delivery lumen configured for fluid        communication with said fuel hose at least during the in-flight        refueling operation, said lumen being configured to enable fuel        to be transferred from the fuel hose to a receiver aircraft        during said in-flight refueling operation;    -   (bbb) a coupling having a hose interface configured for        connecting said lumen to the fuel hose, said coupling configured        for allowing relative rotation between the hose and said body in        at least one degree of freedom while maintaining said fuel        communication.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of the followingfeatures, in any desired combination or permutation:

-   -   (AAA) Wherein said coupling is configured for allowing relative        rotation between the hose and said body in at least two degrees        of freedom.    -   (BBB) Wherein said coupling is configured for allowing relative        rotation between the hose and said body in three degrees of        freedom.    -   (CCC) Wherein said body comprises a boom member having a boom        axis, and wherein said lumen is configured to enable fuel to be        transferred from the fuel hose to a receiver aircraft via said        boom member during said in-flight refueling operation, and/or at        least one said degree of freedom has the respective axis of        rotation generally orthogonal to a plane defining said non-zero        angular disposition between said boom axis and said forward        direction.    -   (DDD) Wherein said coupling comprises a universal coupling.    -   (EEE) Wherein the fuel hose is substantially non-rigid.    -   (FFF) Wherein said boom member is selectively reversibly        telescopically deployable along said boom axis with respect to        said body.    -   (GGG) Wherein said boom member is pivotably mounted to said        body.    -   (HHH) A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between a fuel        delivery end of said boom member and a fuel receptacle of the        receiver aircraft, to enable selectively controlling the        refueling device to provide automatic or autonomous or manual        engagement of the fuel delivery end to the fuel receptacle, said        system optionally comprising an imaging system configured for        providing said data including image data corresponding to a        field of regard aft of the refueling device, and wherein        optionally said imaging system comprises or is operatively        connected to a computing system configured for identifying a        fuel receptacle of a receiver aircraft within said field of        regard from said image data, and for determining a spatial        disposition of said fuel delivery end with respect to the fuel        receptacle.    -   (III) A suitable communication system to transmit image data and        to receive control commands/signals. For example, the        communications system can be operatively connected to the        controller for controlling operation of the refueling device.    -   (JJJ) A spatial control system configured for selectively        ensuring maintaining a desired non-zero angular disposition        between said boom axis and said forward direction at least when        said refueling device is towed by the tanker aircraft in said        forward direction via said fuel hose, and/or, configured for at        least providing directional stability. The spatial control        system according to at least this aspect of the presently        disclosed subject matter can optionally comprise one or more of        features (B) to (L), optionally including one or more of        features (k1) to k(10), mutatis mutandis, in any desired        combination or permutation.    -   (KKK) A force generating arrangement configured for selectively        generating a force along said boom axis in a direction towards        said nozzle. The force generating arrangement according to at        least this aspect of the presently disclosed subject matter can        optionally comprise one or more of features (m1) to (m4),        mutatis mutandis, in any desired combination or permutation.    -   (LLL) A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between a fuel        delivery nozzle of the refueling device and a fuel receptacle of        the receiver aircraft, to enable selectively controlling the        refueling device to provide automatic and/or autonomous and/or        manual engagement of the fuel delivery nozzle to the fuel        receptacle of the receiver aircraft. In at least one example,        the system comprises an imaging system for providing said data        including at least image data corresponding to a field of regard        with respect to the refueling device. The data acquisition        system can be in the form of an imaging system, and can        optionally comprise one or more of features (q1) to (q6),        mutatis mutandis, in any desired combination or permutation.

According to at least one other aspect of the presently disclosedsubject matter, there is provided a refueling system comprising arefueling fuel reservoir connected to a refueling device via a hose, therefueling device being as defined in the examples herein, in particularas defined above and optionally including one or more of the featureslisted above in A to S, AA to LL, and AAA to LLL, in any desiredcombination or permutation. Optionally, the refueling system can behoused in a suitable pod configured to be fixedly attached to a tankeraircraft.

According to at least one other aspect of the presently disclosedsubject matter, there is provided a tanker aircraft comprising at leastone refueling system as defined herein, for example comprising onerefueling system as defined herein, or comprising two refueling systemsas defined herein, or comprising three refueling systems as definedherein, or comprising more four or more refueling systems as definedherein.

According to the tanker aircraft may be a manned tanker aircraft or aUAV, and/or at least one receiver aircraft may be a manned aircraft or aUAV.

Optionally, a tanker aircraft according to the presently disclosedsubject matter can comprise one or two such refueling systems mounted tothe wings (e.g. via pods) and additionally comprise one conventional“flying boom” system in the aft fuselage. Thus, it is readily apparentthat existing tanker aircraft already fitted with conventional “flyingboom” systems can be retrofitted with refueling systems according to thefirst aspect of the presently disclosed subject matter, for example onesuch refueling system fitted onto each wing, thereby effectivelytripling the refueling efficiency/capability of such a tanker aircraft,enabling up to three receiver aircraft having fuel receptacles to berefueled concurrently.

Optionally, a tanker aircraft according to the presently disclosedsubject matter can comprise one or more such refueling systems, as wellas at least one conventional “hose and drogue” system, enabling receiveraircraft of both types to be refueled concurrently.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the presently disclosed subject matter and to seehow it may be carried out in practice, examples will now be described,by way of non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a top view of an example of a tanker system according to thepresently disclosed subject matter.

FIG. 2 is a side view of the tanker system of FIG. 1.

FIG. 3 is an isometric view of an example of a refueling deviceaccording to the presently disclosed subject matter.

FIG. 4 is a side view of the refueling device of FIG. 3.

FIG. 5 is a top view of the refueling device of FIG. 3.

FIG. 6( a) is a front view of the refueling device of FIG. 3; FIG. 6( b)is an aft view of the refueling device of FIG. 3.

FIG. 7 is a cross-sectional side view of the refueling device of FIG. 5taken along B′-B′.

FIG. 8 is a cross-sectional side view of the refueling device of FIG. 4taken along A′-A′.

FIG. 9( a) is an isometric view of the refueling device of FIG. 3, withthe airbrakes and boom member in the deployed positions; FIG. 9( b) is atop view of the refueling device of FIG. 9( a).

FIG. 10 is a partial side view of the boom member of the refuelingdevice of FIG. 3 in proximity to a fuel receptacle of a receiveraircraft.

FIG. 11 is an isometric view of the refueling device of FIG. 3, furtherschematically illustrating a volume aft thereof.

FIGS. 12( a) to 12(d) are respective isometric, side, top and frontviews of an alternative variation of the example of refueling device ofFIG. 3.

FIGS. 13( a) to 13(d) are respective isometric view of other alternativevariations of the example of refueling device of FIG. 3.

FIG. 14 is an isometric view of another alternative variation of theexample of refueling device of FIG. 3.

FIGS. 15( a) and 15(b) are respective isometric view of otheralternative variations of the example of refueling device of FIG. 3.

FIGS. 16( a) to 16(d) illustrated another alternative variation of theexample of refueling device of FIG. 3, in isometric view, top view, sideview and aft view, respectively.

FIGS. 17( a) to 17(d) illustrated another example of a refueling deviceaccording to the presently disclosed subject matter, in isometric view,side view, top view and front view, respectively.

FIG. 18 is a block diagram schematically illustrating a system forcontrolling in-flight refueling, according to certain examples of thepresently disclosed subject matter;

FIG. 19 is a flowchart illustrating a sequence of operations carried outfor performing in-flight refueling, according to certain examples of thepresently disclosed subject matter;

FIG. 20 is a flowchart illustrating a sequence of operations carried outfor providing maneuvering commands for positioning a receiver aircraftwithin an engagement area related thereto, according to certain examplesof the presently disclosed subject matter;

FIG. 21 is a flowchart illustrating a sequence of operations carried outfor providing steering commands to a refueling device for maneuvering toan engagement enabling position, according to certain examples of thepresently disclosed subject matter;

FIG. 22 is a flowchart illustrating a sequence of operations carried outfor determining the receiver aircraft spatial disposition with respectto the engagement area related thereto, according to certain examples ofthe presently disclosed subject matter;

FIG. 23 is a flowchart illustrating a sequence of operations carried outfor determining the refueling device spatial disposition with respect tothe engagement enabling position, according to certain examples of thepresently disclosed subject matter;

FIG. 24 is an illustration of an example of a receiver aircraftpositioned outside a virtual engagement area, according to certainexamples of the presently disclosed subject matter;

FIG. 25 is an illustration of an example of a receiver aircraftpositioned inside a virtual engagement area, according to certainexamples of the presently disclosed subject matter;

FIG. 26 is an illustration of an example of a refueling device not in anengagement enabling position, according to certain examples of thepresently disclosed subject matter;

FIG. 27 is an illustration of an example of a refueling devicepositioned in an engagement enabling position, according to certainexamples of the presently disclosed subject matter;

FIG. 28 is an illustration of an example of a sensed image indicatingthat the refueling device is not positioned in an engagement enablingposition, according to certain examples of the presently disclosedsubject matter;

FIG. 29 is an illustration of an example of a sensed image indicatingthat the refueling device is positioned in an engagement enablingposition, according to certain examples of the presently disclosedsubject matter;

DETAILED DESCRIPTION

In the drawings and descriptions set forth, identical reference numeralsindicate those components that are common to different embodiments orconfigurations.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “steering”, “determining”,“calculating”, “providing”, “causing”, “activating”, “receiving”,“acquiring”, “comparing”, “obtaining”, or the like, include actionand/or processes of a computer that manipulate and/or transform datainto other data, said data represented as physical quantities, e.g. suchas electronic quantities, and/or said data representing the physicalobjects. The term “computer” should be expansively construed to coverany kind of electronic device with data processing capabilities,including, by way of non-limiting example, a personal computer, aserver, a computing system, a communication device, aprocessor/processing unit (e.g. digital signal processor (DSP), amicrocontroller, a microprocessor, a field programmable gate array(FPGA), an application specific integrated circuit (ASIC), etc.), anyother electronic computing device, and or any combination thereof.

The operations in accordance with the teachings herein may be performedby a computer specially constructed for the desired purposes or by ageneral purpose computer specially configured for the desired purpose bya computer program stored in a computer readable storage medium.

As used herein, the phrase “for example,” “such as”, “for instance” andvariants thereof describe non-limiting embodiments of the presentlydisclosed subject matter. Reference in the specification to “one case”,“some cases”, “other cases”, “one example”, “some examples” or variantsthereof means that a particular feature, structure or characteristicdescribed in connection with the embodiment(s) is included in at leastone embodiment of the presently disclosed subject matter. Thus theappearance of the phrase “one case”, “some cases”, “other cases”, “oneexample”, “some examples” or variants thereof does not necessarily referto the same embodiment(s).

It is appreciated that certain features of the presently disclosedsubject matter, which are, for clarity, described in the context ofseparate embodiments, may also be provided in combination in a singleembodiment. Conversely, various features of the presently disclosedsubject matter, which are, for brevity, described in the context of asingle embodiment, may also be provided separately or in any suitablesub-combination.

In embodiments of the presently disclosed subject matter, fewer, moreand/or different stages than those shown in FIGS. 19 to 23 can beexecuted. In embodiments of the presently disclosed subject matter oneor more stages illustrated in FIGS. 19 to 23 can be executed in adifferent order and/or one or more groups of stages may be executedsimultaneously. FIGS. 7 and 18 illustrate a general schematic of thesystem architecture in accordance with an embodiment of the presentlydisclosed subject matter. Each module in FIGS. 7 and 18 can be made upof any combination of software, hardware and/or firmware that performsthe functions as defined and explained herein. The modules in FIGS. 7and 18 can be centralized in one location or dispersed over more thanone location. In other embodiments of the presently disclosed subjectmatter, the system may comprise fewer, more, and/or different modulesthan those shown in FIGS. 7 and 18.

According to a first aspect of the presently disclosed subject matter,there are provided systems and devices for in-flight refueling ofaircraft.

Referring to FIGS. 1 and 2, a tanker system according to one example ofthe presently disclosed subject matter, generally designated 10,comprises a tanker aircraft 12 comprising one or more in-flightrefueling systems 50. In this example, the tanker aircraft 12 has threesuch in-flight refueling systems 50, one comprised on each one of theport wing 14 and starboard wing 16, and a third one comprised on therear portion of the fuselage 15, and the tanker aircraft 12 isconfigured for in-flight concurrent refueling of up to three receiveraircraft 20. In alternative variations of this example the tankeraircraft 12 can have at least one, or two, or more than three in-flightrefueling systems 50, arranged in any suitable configuration withrespect to the tanker aircraft 12.

By way of non-limiting example, such a tanker aircraft 12 can be asuitably equipped Boeing 767 and each receiver aircraft 20 can includeany one of suitably equipped F-15, or F-16, or B2 stealth bomber, orother suitably equipped fighter, bomber or other aircraft.Alternatively, and also by way of non-limiting example, the tankeraircraft may be a UAV, and/or at least one of the receiver aircraft maybe a UAV.

Also by way of non-limiting example, a refueling flight envelope for usewith such a tanker system can include a forward speed of between about220 knots and about 320 knots (typically about 280 knots), and analtitude of between 500 ft and between about 30,000 ft and about 40,000ft, and in general not below about 10,000 ft, in which refueling cantake place between the tanker aircraft 12 and each receiver aircraft 20,flying in formation, depending on the operating limits of the tankeraircraft and of the receiver aircraft, as well as other factors.

Each in-flight refueling system 50 comprises an elongate, non-rigid,fuel delivery hose 52, reversibly extendible from the tanker aircraft12. A first end (not shown) of the hose 52 is connected to a refuelingfuel tank (not shown) carried by the tanker aircraft 12. For example,such a refueling fuel tank can be an internal fuel tank of the tankeraircraft 12, for example the tanker aircraft's own fuel tanks, or aspecial fuel reservoir mounted internally in the tanker aircraft 12, forexample in the fuselage, or externally and carried in fuel pods, forexample.

The hose 52 is flexible and can be retracted into a roll up drum (notshown), suitably provided in the tanker aircraft 12, and selectivelydeployed therefrom when required.

The second (aft) end 54 of hose 52 is operatively connected to arespective refueling device that is towed in a forward direction A bythe tanker aircraft 12 via hose 52 when the hose 52 is extended and thetanker aircraft 12 is in flight.

In this example, one in-flight refueling system 50 is centrally-locatedand mounted with respect to the rear fuselage of the tanker aircraft 12,and each of the other two in-flight refueling systems 50 is comprised ina respective pod 51 that is attached to the underside of the respectivewing.

FIGS. 3 to 11 illustrate a refueling device according to a first exampleof the presently disclosed subject matter, generally designated 100, foruse with an in-flight refueling system, for example at least one of thein-flight refueling systems 50 illustrated FIGS. 1 and 2.

For convenience, and referring to FIG. 3 for example, a roll axis R, apitch axis P and a yaw axis Y can be conventionally defined with respectto the refueling device 100. The roll axis R is parallel to or co-axialwith the longitudinal axis of the device 100; the pitch axis P isgenerally in lateral and orthogonal relationship to the roll axis R(i.e., parallel to the horizontal when the body is at a zero rollangle); and yaw axis Y is in orthogonal relationship to the roll axis Rthe pitch axis P (i.e., parallel to the vertical when the body is at azero pitch angle).

Refueling device 100 is affixed to the end 54 of hose 52 and comprisesan elongate body 110 comprising a longitudinal axis 111 and a generaloval cross section (as best seen in FIGS. 6( a) and 6(b)), although inalternative variations of this example the body 110 can have anysuitable cross-sectional shape, for example circular cross-section,polygonal cross-section, and so on. Referring in particular to FIGS. 7and 8, the body 110 comprises a fuel delivery lumen 120 and a boommember 130 (which at least in the disclosed examples is a substantiallyrigid boom member) in fluid communication therewith. The boom member 130defines a boom axis 131 and comprises a fuel delivery nozzle 135 at aterminus 136 of the boom member 130. The nozzle 135 is configured forreversibly engaging with the fuel receptacle 22 of a receiver aircraft20 (see also FIGS. 1, 2 and 11), and thus can comprise any conventionaldesign of such nozzles, which are well known, or indeed can comprise anyother current or future design of such an in-flight refueling nozzle.

The boom member 130 is telescopically mounted to body 110, and isreversibly extendable from a stowed position illustrated in FIGS. 3 to 8in which most of the boom member 130 is accommodated in a sleeve withinthe body 110, to the fully extended position illustrated in FIGS. 9( a)and 9(b), by means of a controllable actuation mechanism (not shown).Optimally, the boom member 130 is telescopically extendable to acontrollably variable extended position in a general aft direction fromthe aft end 112 of body 110, up to the aforesaid the fully extendedposition. While in this example the boom axis 131 is parallel andco-axial with longitudinal axis 111, in at least some alternativevariations of this example the boom axis can be parallel but notco-axial with the body longitudinal axis, or the boom axis can benon-parallel with respect to the body longitudinal axis.

In an alternative variation of this embodiment, the boom member 130 ispermanently extended with respect to the body 110, and is nottelescopically or reversibly extendible therefrom. In anotheralternative variation of this example, the boom member 130 ispermanently retracted with respect to the body 110, and is nottelescopically or reversibly extendible therefrom, and thus may onlycomprise a relatively short section extending aft from the body 110 toconnect to the nozzle 135.

In alternative variations of this example, or in other examples, theboom member may have any other suitable structure configured forcoupling with the receiver aircraft, in particular the fuel receptaclethereof.

The body 110 comprises a coupling 140 at forward end 114 thereof. Thecoupling 140 comprises a hose interface 142 configured for connectingthe lumen 120 to the hose 52, and thereby to the tanker aircraft 12. Thecoupling 140 is configured for allowing relative rotation between thebody 110 and the hose 52 while maintaining fluid communication betweenthe lumen 120 and the hose 52 and thus the refueling tank. In thisexample, the coupling 140 is in the form of a universal joint or thelike (also referred to as a universal coupling, a Cardan joint, aHardy-Spicer joint or a Hooke's joint, and so on), and is thusconfigured for allowing relative rotation between the body 110 and thehose 52 in three degrees of freedom. In alternative variations of thisexample and in other examples, the coupling can instead be configuredfor allowing relative rotation between the body 110 and the hose 52 inone degree of freedom, or in two degrees of freedom. In particular, thecoupling allows the body 110, and in particular the boom member 130 andthe boom axis 131 to freely pivot with respect to the hose 52, inparticular the second end 54, about at least one axis B (see FIGS. 3 and5, for example), so that the spatial orientation of the refueling device100 can be controllably changed without significant mechanicalresistance thereto being generated by the hose 52 about axis 13, whichis typically parallel the pitch axis P of the refueling device 100, butmay be alternatively inclined to the pitch axis P and/or to the rollaxis R and/or to the yaw axis Y.

The body 110 can optionally be formed as an integral and/or unitarystructure incorporating the boom member 130 and the coupling 140.

In alternative variations of this example the coupling 140 can beomitted and replaced with a fixed coupling that is configured tomaintain a fixed relative spatial disposition between the body 110 andthe hose 52 while maintaining fluid communication between the lumen 120and the hose 52. For example such a spatial disposition may be an angleφ (see FIG. 1) of about 0°; or about 30°; or in a range between about 5°and about 85°; or in a range between about 10° and about 80°; or in arange between about 15° and about 70°; or in a range between about 20°and about 60°; or in a range between about 25° and about 50°; or in arange between about 20° and about 40°; or in a range between about 25°and about 40°; or in a range between about 28° and about 32°.

The refueling device 100 further comprises a spatial control system 160,configured for controlling a spatial disposition of the refueling device100 when towed aft of the tanker aircraft 12 via the hose 52, andenables the refueling device 100 to be steered and/or to adopt anydesired stable spatial disposition while being towed at the end 54 ofhose 52.

In particular, spatial control system 160 is configured for selectivelyand controllably providing a non-zero angular disposition, angle θ,between the boom axis 131 and the forward direction A, and enables thisangle θ to be selectively maintained between the boom axis 131 and theforward direction A at least for a part of the time when the refuelingdevice 100 is being towed by the tanker aircraft 12 via hose 52, inparticular during the engagement operation of the fuel device 100 to thereceiver aircraft 20 and during refueling thereof. In particular, angleθ is in pitch, i.e., about a pitch axis P of the refueling device 100and is defined on a plane including the roll axis R and the yaw axis Yof the refueling device 100. Angle θ is thus representative of an angleof attack of the refueling device 100 in the airflow, or at least of theboom axis 131 with respect to forward direction A (which is typically,but not exclusively, parallel to the horizontal direction).Nevertheless, and depending on specific conditions during any particularrefueling operation, angle θ can include an angular displacementcomponent between the boom axis 131 and the forward direction A in yaw(i.e., about yaw axis Y), for example due to sideslip angle, and/or inroll (i.e. about roll axis R), instead of or in addition to an angulardisplacement component in pitch (i.e., about pitch axis P).

The refueling device 100, in particular the boom member 130, nozzle 135and lumen 120 can be sized to allow suitable fuel flow rates forrefueling a wide range of receiver aircraft. By way of non-limitingexample, relative high fuel flow rates (for example up to 1000 USgallons/6,500 lb per minute) can be provided for refueling operations oflarge aircraft (for example transport aircraft, bombers, etc), while forfighter aircraft that cannot accept fuel at the maximum flow rate of therefueling device 100, the refueling pressure can be correspondinglyreduced. Alternatively the refueling device 100, in particular the boommember 130, nozzle 135 and lumen 120 can be sized to allow suitable fuelflow rates for refueling a narrow range of receiver aircraft., forexample only fighter aircraft or only larger aircraft (for example about400 US gallons/2,600 lb per minute).

Thus, the spatial control system 160 is configured for providingstability to the refueling device 100, while tethered to and towed bythe tanker aircraft 12 via the hose 52, and while the boom axis 131 isat any desired pitch and/or yaw and/or roll angle corresponding to theaforesaid angle θ.

In particular, and referring to FIG. 10, angle θ is such as to provide adesign angle (angle θ_(des)) that is within a particular angular rangewhich corresponds to the design relative angular position of the boommember 130 (and boom axis 131) with respect to the receiver aircraft 20.

In particular, design angle θ_(des) is the design relative angularposition of the boom axis 131 with respect to the longitudinal axis ofthe receiver aircraft 20 (the receiver aircraft 20 being at apredetermined spatial orientation relative to the forward direction,typically in horizontal forward flight), to enable the boom member 130to align and engage the nozzle 135 with respect to the fuel receptacle22. Thus, angle θ (which can have an angular component in yaw and/or inpitch and/or in roll) compensates for any off-nominal pitch of thereceiver aircraft 20 (for example if the receiver aircraft 20 istraveling along direction A at a non-zero angle of attack) and/or forany off-nominal roll of the receiver aircraft 20 (for example if thereceiver aircraft 20 is traveling along direction A at a non-zero rollangle) and/or for any off-nominal yaw of the receiver aircraft 20 (forexample if the receiver aircraft 20 is traveling along direction A at anon-zero sideslip angle) to ensure that the actual angular dispositionbetween the boom axis 131 and the receiver aircraft longitudinal axis ismaintained at design angle θ_(des) even as the relative spatialorientation between the receiver aircraft 20 and the forward directionchanges.

Thus, design angle θ_(des) the boom axis 131 is in an engagementenabling orientation with respect to the receiver aircraft 20, and inparticular with respect to the fuel receptacle 22.

In non-limiting examples, angle θ (and in particular angle θ_(des)) canbe in a range between about 5° and about 85°; or in a range betweenabout 10° and about 80°; or in a range between about 15° and about 70°;or in a range between about 20° and about 60°; or in a range betweenabout 25° and about 50°; or in a range between about 20° and about 40°;or in a range between about 25° and about 40°; or in a range betweenabout 28° and about 32°.

In one non-limiting example, angle θ_(des) can be about 30°, andoperation of the refueling device 100 to adopt this angle automaticallyrenders it compatible for use with existing receiver aircraft 20, inwhich the fuel receptacles 22 are configured for receiving and engagingwith a nozzle at the end of a boom where the boom is at about 30° to thelongitudinal axis of the receiver aircraft, without the need formodifying the configuration of the fuel receptacle thereof.

Thus, when angle θ is equal to design angle θ_(des), the receiveraircraft travelling along direction A with zero angle of attack and zerosideslip and zero roll, and boom axis 131 is at the required spatialorientation to the forward direction A of the tanker aircraft and thereceiver aircraft such as to ensure engagement between the nozzle 135 inthe fuel receptacle 22, without the need for modifying the configurationof the fuel receptacle thereof.

In this example, the spatial control system 160 comprises a selectivelycontrollable aerodynamic control system 170, comprising a forward set172 of aerodynamic control surfaces 173 mounted to body 110 at a forwardportion thereof, and an aft set 174 of aerodynamic control surfaces 175mounted to the body 110 at an aft portion thereof. Referring inparticular to FIG. 4, the aft set 174 is thus in aft spaced relationshipwith respect to the forward set 172, and the center of gravity CG of thebody 110 is disposed longitudinally intermediate the aft set 174 and theforward set 172, noting that the actual longitudinal position of thecenter of gravity CG can shift between two extreme longitudinalpositions according to, inter alga, whether the boom member 135 isextended or retracted, and whether fuel is present in the refuelingdevice 100 or absent therefrom. In alternative variations of thisexample and in other examples, the center of gravity can be forward ofboth the forward set and the aft set of aerodynamic surfaces, which areconfigured to provide the required stability to the refueling device 100with the boom axis 131 at any desired pitch and/or yaw and/or rollangle.

In this example, the forward set 172 comprises four aerodynamic controlsurfaces 173 in cruciform “X” configuration (see in particular FIGS. 6(a) and 6(b)). Each aerodynamic control surface 173 is in the form of avane, pivotably mounted to the body 110 via a respective boss 183laterally projecting from the surface of body 110. Each boss 183 housesan actuator (not shown) for controlling the angular position of therespective vane about a respective pivot axis, and is controlled bycontroller 180. The pivot axes of the vanes are, in at least thisexample, orthogonal to at least one of longitudinal axis 111 and boomaxis 135, and can also intersect the respective at least one oflongitudinal axis 111 and boom axis 135.

In this example, controller 180 comprises any suitable computer controlsystem, and is housed in the refueling device 100 (see FIG. 7). Inalternative variations of this example and in other examples, thecontroller 180 or portions thereof can instead comprise any suitableelectronic control unit, or any other suitable control unit.Additionally or alternatively, the controller or portions thereof can becomprised elsewhere in the in-flight refueling system 50 or in thetanker aircraft 12.

In this example, the aft set 174 comprises two aerodynamic controlsurfaces 175 in “Vee” configuration (see in particular FIGS. 6( a) and6(b)). Each aerodynamic control surface 175 is in the form of a vane,pivotably mounted to the body 110 via a respective boss 186 laterallyprojecting from the surface of body 110. Each boss 186 houses anactuator (not shown) for controlling the angular position of therespective vane, and is also controlled by controller 180.

In this example, and referring in particular to FIG. 4, each boss 183has an aerofoil-shaped cross section defining a chord 185, and each boss186 has an aerofoil-shaped cross section defining a chord 185.Furthermore the chord 185 is oriented with respect to at least one ofthe longitudinal axis 111 and the boom axis 131 such as to align thechord 185 with the forward direction A, which is nominally the airflowdirection with respect to the refueling device 100, when the refuelingdevice 100 is at spatial orientation in which the boom axis 131 is atangle θ_(des) with respect to the forward direction A. Similarly, eachchord 185 is oriented with respect to at least one of the longitudinalaxis 111 and the boom axis 131 such as to align the chord 185 with theforward direction A when the refueling device 100 is at spatialorientation in which the boom axis 131 is at angle θ_(des) with respectto the forward direction A.

In alternative variations of this example or in other examples, theforward set aerodynamic control surfaces can comprise two or three orfour or more than four vanes (or any other type of aerodynamic controlsurfaces), in any suitable configuration, including for example fourvanes in cruciform “+” configuration, and/or, each vane (or other typeof aerodynamic control surfaces) can be pivotable about a respectiveaxis having any suitable spatial relationship with respect to thelongitudinal axis of the refueling device and/or the axis of the boommember. Additionally or alternatively, the aft set aerodynamic controlsurfaces can comprise two more than two vanes (or any other type ofaerodynamic control surfaces), in any suitable configuration.Additionally or alternatively, the respective aerodynamic controlsurfaces of the spatial control system, in the form of pivotable vanesor any other suitable configuration, are mounted to respective bosses,which can be aerodynamically shaped but at a different orientation withrespect to the longitudinal axis 111 and/or the boom axis 131, orwherein the respective bosses can have a different shape, for example inthe form of cylinders or any other prismatic shape or other shape, orwherein the respective aerodynamic control surfaces are directly mountedto the body 110 without bosses (in which case the respective actuatorscan be provided in the body 110).

For example, one such alternative variation of the refueling deviceexample of FIGS. 3 to 11 is illustrated in FIGS. 12( a) to 12(d), inwhich the respective example of the refueling device, designated 1000,comprises all the elements and features of the refueling device 100,mutatis mutandis, with the main difference that the aerodynamic controlsystem 170 of the example of the refueling device 100 is replaced withan alternative configuration for the spatial control system 160,comprising aerodynamic system 1170. Thus, the refueling device 1000comprises a body 1110, forward end 1114, aft end 1112, longitudinal axis1111, fuel delivery lumen (not shown), boom member 1130, boom axis 1131,fuel delivery nozzle 1135, terminus 1136, coupling 1140, hose interface1142, substantially similar to the corresponding components as describedherein for the example of the refueling device 100 or alternativevariations thereof, mutatis mutandis, i.e., respectively: body 110,forward end 114, aft end 112, longitudinal axis 111, fuel delivery lumen120, boom member 130, boom axis 131, fuel delivery nozzle 135, terminus136, coupling 140, hose interface 142. In addition, the refueling device1000 optionally comprises a force generating arrangement (not shown) forexample substantially similar to force generating arrangement 190 asdescribed hereinbelow, mutatis mutandis, and/or a suitable dataacquisition system (not shown) for example substantially similar toimaging system 150, as described hereinbelow, mutatis mutandis, and/or acontroller 1180, for example similar to controller 180 as describedherein, mutatis mutandis, and/or a control computer system (not shown),for example similar to control computer system 155 as described herein,mutatis mutandis.

The aerodynamic system 1170 comprises a forward set 1172 of aerodynamiccontrol surfaces 1173 mounted to body 110 at a forward end 1114 thereof,and an aft set 1174 of aerodynamic control surfaces 1175 mounted to thebody 1110 at an aft portion 1112 thereof. The aft set 1174 is thus inaft spaced relationship with respect to the forward set 1172, and thecenter of gravity of the body 1110 is disposed longitudinallytherebetween, though in alternative variations of this example and inother examples, the center of gravity can be forward or aft of both theforward set and the aft set of aerodynamic surfaces, which areconfigured to provide the required stability to the refueling device1000 with the boom axis 1131 at any desired pitch and/or yaw and/or rollangle.

In this example, the forward set 1172 comprises four aerodynamic controlsurfaces 1173 in cruciform “+” configuration, and each aerodynamiccontrol surface 1173 is in the form of a vane, pivotably mounted to thebody 1110 and operatively connected to an actuator system (not shown)for controlling the angular position of the respective vane about arespective pivot axis, and is controlled by controller 1180. The pivotaxes of the vanes are, in at least this example, orthogonal to at leastone of longitudinal axis 1111 and boom axis 1135, and can also intersectthe respective at least one of longitudinal axis 1111 and boom axis1135. In alternative variations of this example, the forward set 1172may comprise any suitable configuration or vanes, wings, RCS, etc.

In this example, the aft set 1174 comprises a high H-tail configuration,comprising two vertical stabilizers 1175, one on either side of ahorizontal stabilizer 1171, which in turn is mounted to the upper sideof the aft end 1112. Each vertical stabilizer 1175 comprises acontrollably pivotable rudder 1178, and the horizontal stabilizer 1171comprises a pair of pivotable elevators 1179, which are controllablyactuated by an actuator system (not shown) also controlled by controller1180.

For example, four other such alternative example variations areillustrated in FIG. 13( a) to FIG. 13( d), respectively, in which forthe respective refueling devices 100″a, 100″b, 100″c and 100″d,respectively, the respective forward set 172″ comprises two aerodynamiccontrol surfaces 173″ in “Vee” configuration, and the respective aft set174″ comprises two aerodynamic control surfaces 175″ in “Vee”configuration as in the first example, mutatis mutandis. In the exampleof FIG. 13( a) the aerodynamic control surfaces 173″ are smaller thanthe aerodynamic control surfaces 175″, while in the examples of FIG. 13(b) to FIG. 13( d) the aerodynamic control surfaces 173″ are the samesize nominally as the aerodynamic control surfaces 175″. In yet otheralternative variations of the example of FIGS. 13( a) to 13(d), theaerodynamic control surfaces 173″ are larger than the aerodynamiccontrol surfaces 175″.

For example, another such alternative example variation is illustratedin FIG. 14, in which the respective aft set 174′ for the refuelingdevice 100′ comprises three aerodynamic control surfaces, twoaerodynamic control surfaces 175′ in “Vee” configuration as in the firstexample, mutatis mutandis, and a third vane 175″ in vertical anddownwardly depending relationship with respect to the respective body110′.

For example, two such alternative example variations are illustrated inFIGS. 15( a) and 15(b) in which the respective forward set 172′″ foreach respective refueling device 100′″a, 100′″b comprises twoaerodynamic control surfaces 173″ with zero dihedral, and the respectiveaft set 174′″ also comprises two aerodynamic control surfaces 175′ withzero dihedral. In the example of FIG. 15( b), each aerodynamic controlsurfaces 175′″ further comprises a vertical vane 176′ in upwardlydepending relationship with respect to the aerodynamic control surfaces175′″ at the respective wing tips.

For example, in the alternative example variations illustrated in FIGS.13( a), 13(c) and 13(d), the respective forward aerodynamic controlsurfaces 173″ are pivotably mounted to cylindrically shaped bosses 183″,and the respective aft aerodynamic control surfaces 175″ are pivotablymounted to cylindrically shaped bosses 185″. On the other hand, in theexamples illustrated in FIGS. 13( b), 15(a) and 15(b), the respectiveforward and aft aerodynamic control surfaces are pivotably mounteddirectly to the body of the respective refueling device.

Referring again to the example of FIGS. 3 to 10, the aerodynamic controlsystem 170 is configured for allowing the refueling device 100 to adoptany desired angle θ while maintaining a zero pitching moment (and/orzero yawing moment and/or zero rolling moment), as the forward set 172of aerodynamic control surfaces 173 is configured for trimming anypitching moment (and/or yawing moment and/or rolling moment,respectively) generated by aft set 174 of aerodynamic control surfaces175 at a given pitch angle (and/or yaw angle and/or roll angle,respectively) of the body 110, or vice versa. In this example, where thecenter of gravity CG is longitudinally intermediate the forward set 172and the aft set 174, the trimming pitching moment generated by theforward set 172, for example is in a counter-rotational direction withrespect to the pitching moment generated by aft set 174 to maintain aparticular pitch angle for angle θ, while the pitch forces generated byforward set 172 and the aft set 174 are in the same direction. Inalternative variations of this example or in other examples in which thecenter of gravity of the refueling device is forward of both the forwardset and the aft set of aerodynamic control surfaces, the trimmingpitching moment generated by the forward set of aerodynamic controlsurfaces, for example, is also in a counter-rotational direction withrespect to the pitching moment generated by aft set of aerodynamiccontrol surfaces to maintain a particular pitch angle for angle θ, butthe pitch forces generated by forward set of aerodynamic controlsurfaces and the aft set of aerodynamic control surfaces are in oppositedirections. In yet other examples, the refueling device comprises thespatial control system in the form of a single set of aerodynamiccontrol surfaces which are configured for generating zero pitch momentfor a desired range of pitch angles corresponding to angle θ, and thespatial control system is self-trimming to provide stable pitch anglecorresponding to angle θ.

In the first example, the aft aerodynamic control surfaces 175 arelarger than the forward aerodynamic control surfaces 173, though inalternative variations of this example and in other examples, the aftaerodynamic control surfaces 175 can be the same size or smaller thanthe forward aerodynamic control surfaces 173.

In other variations of this example and in other examples, the spatialcontrol system 160 comprises a non-adjustable aerodynamic control systemthat is configured for allowing the refueling device 100 to adopt aparticular, pre-set, desired angle θ while maintaining a zero pitchingmoment (and/or zero yawing moment and/or zero rolling moment), thisbeing the design angle θ_(des), at least at one set of conditionsassociated with the refueling—for example at a particular forward speedand altitude. Thus, once the refueling device is towed behind the tankeraircraft 12 via the hose 52, the boom axis automatically adopts theparticular design angle θ_(des), and stably maintains this relativespatial disposition at the aforesaid set of conditions until therefueling device is retracted back into the tanker aircraft 12.

In other variations of this example and in other examples, the spatialcontrol system 160 comprises a selectively controllable control systemthat is not based on aerodynamic control surfaces. For example, aplurality of suitable thrust nozzles or other suitable reaction controlthruster system (RCS) can be mounted to the body to provide thrustvector control and maintain the boom axis 131 at any desired angle θ.Such thrusters or RCS can be operatively connected to a suitablecompressed air supply or compressed gas supply, for example carried bythe refueling device itself, or carried by the tanker aircraft andsupplied to the refueling device via pneumatic or gas lines, orgenerated by the tanker aircraft and/or the refueling device using asuitable compressor taking air from the atmosphere.

Referring in particular to FIGS. 3, 4, 5, 9(a), 9(b) and 10, therefueling device 100 further comprises a force generating arrangement190. The force generating arrangement 190 is configured for selectivelygenerating a force F (FIGS. 9( a) to 11) along the boom axis 131 in adirection towards nozzle 135. In this example, the force generatingarrangement 190 selectively generates force F as a drag, and is in theform of a selectively and reversibly deployable drag inducingarrangement 192, comprising a selectively and reversibly deployable airbrake system 194. The air brake system 194 comprises a port air brake195 and a starboard air brake 196, each comprising a curved plate 197pivotably hinged laterally to the body 110 via hinges 198 between aclosed position, in which the plate is received in a recess 199 (bestseen in FIGS. 9( a) and 9(b)) and the outer surface of the plate 197 isflush with the outer surface of body 110, and an open position in whichthe plate offers a maximum frontal surface area to the airflow andthereby generates drag. The hinges 199 are forwardly disposed so thatthe convex outer surface of each one of the port air brake 195 and ofthe starboard air brake 196 faces the airflow. Suitable actuators (notshown) are operatively connected to and operate the air brakes 195, 196,controlled by controller 180. Alternatively, and as illustrated for theexample of FIG. 13( a), the hinges 199 can be disposed aft of therespective plates 197 so that the convex outer surface of each one ofthe port air brake 195 and the starboard air brake 196 faces away fromthe airflow. In the example of FIG. 13( d) the force inducingarrangement 190 is an airbrake in the form of plate 920 that isselectively laterally deployable and retractable with respect toairbrake housing 910.

The force generating arrangement 190 is in particular configured forselectively generating a force F having a magnitude sufficient forforcing the nozzle 135 into engagement with the fuel receptacle 22 ofthe receiver aircraft (FIG. 11) when the nozzle 135 (and the boom member130) and the fuel receptacle 22 are in a predetermined relative spatialdisposition, i.e., when the refueling device 100 reaches an engagementenabling position and the boom axis is in the engagement enablingorientation with respect to the receiver aircraft 20, and in particularwith respect to the fuel receptacle 22.

The force generating arrangement 190 is further configured forselectively operating in this manner responsive to the nozzle 135 beingin a predetermined proximity to the fuel receptacle 22, i.e. responsiveto the nozzle 135 being in a predetermined spacing with respect to thefuel receptacle 22, typically the engagement enabling spatial position,and can be operated manually or automatically to provide such a force F,as will become clearer herein.

Thus, at the engagement enabling position, when the boom member 130, orthe boom axis 131, is in a predetermined spatial disposition withrespect to the fuel receptacle 22 and the nozzle 135 being in apredetermined spacing with respect to the fuel receptacle 22 (i.e., atthe engagement enabling position the boom axis is at the engagementenabling orientation—corresponding to the design angle θ_(des)), theforce generating arrangement 190 can be selectively actuated to compelthe boom member 130 to follow a predetermined trajectory, for examplealigned with the boom axis 131 in the direction of the receiver aircraft20, to ensure alignment and engagement between the nozzle 135 and thefuel receptacle 22. In this example, the boom 130 is telescopicallyextended to the extended position in a direction along the boom axis131, which is maintained at the engagement enablingorientation—corresponding to the design angle θ_(des), while the body110 remains at the same spatial disposition with respect to the receiveraircraft 20. In alternative variations of this example, the boom 130 ispartially or fully telescopically extended towards the receiver aircraft20 while the device 100 can be moved towards or away from the receiveraircraft 20 to effect engagement between the nozzle 135 and the fuelreceptacle 22. In other alternative variations of this example, the boommember 130 remains retracted, and the body 110 itself is moved towardsthe receiver aircraft 20 along a the direction of the boom axis,maintaining the boom axis 131 at the engagement enablingorientation—corresponding to the design angle θ_(des), to effectengagement between the nozzle 135 and the fuel receptacle 22.

Once the nozzle 135 is forced into engagement with the fuel receptacle22 of the receiver aircraft 20, the tanker aircraft 12 can beginrefueling the receiver aircraft 20.

In alternative variations of this example and in other examples, theforce generating arrangement 190 can comprise any other suitable draginducing arrangement, for example spoilers on the vanes 175.

In yet other variations of this example and in other examples, the forcegenerating arrangement 190 can be configured for generating a thrustforce in the required direction. For example, one or a plurality ofsuitable thrust nozzles can be mounted to the body to provide therequired thrust vector parallel to the boom axis 131 towards nozzle 135.Such thrust nozzle(s) can be operatively connected to a suitablecompressed air or compressed gas supply, for example carried by therefueling device itself, or carried by the tanker aircraft and suppliedto the refueling device via pneumatic or gas lines, or generated by thetanker aircraft and/or the refueling device.

In yet other alternative variations of this example and in otherexamples, the force generating arrangement can be omitted, and forexample the receiver aircraft and/or the boom member can comprisesuitable means for mechanically engaging the nozzle to the fuelreceptacle that does not require such a force F to be generated by thedevice 100. For example, the fuel receptacle can comprise a suitablemechanical clamp that engages the terminus 136 of the boom member 130,and pulls in the nozzle 135 into engagement with the fuel receptacle 22.

Referring in particular to FIGS. 4, 5, 10 and 11 the refueling device100 further comprises a suitable data acquisition system for providingor enabling the calculation of spatial data relating to the relativespatial dispositions between the refueling device 100 and the receiveraircraft 20, in particular the relative spatial dispositions between thefuel delivery nozzle of the refueling device 100 and the fuel receptacleof the receiver aircraft, to enable selectively controlling therefueling device to provide automatic (optionally including autonomous)and/or manual steering of the refueling device 100 to the engagementenabling position and subsequent selective engagement of the fueldelivery nozzle to the fuel receptacle of the receiver aircraft. Atleast in the example of FIGS. 4, 5, 10 and 11, the data acquisitionsystem is in the form of imaging system 150, in particular configuredfor providing imaging data of any object coming within a field of regard(FOR) aft of the refueling device 100. Such a field of regard has apredetermined depth aft of the imaging system and in this examplecomprises sensing volume 159 aft of the imaging system 150, which whilein this example comprises a prismoidal volume in alternative variationsof this example the FOR can have any suitable shape, for exampleconical, frustoconical, cylindrical, spherical, part-spherical (e.g.hemispherical), parallelepiped (for example cubic) or any other regularor irregular shape. The sensing volume 159, i.e., the predetermineddepth of the FOR, extends aft further than is required corresponding tothe engagement enabling position, i.e., further than the maximumextension of the boom member 130 when this is in its fully deployedposition. The imaging system 150 is operatively connected to a controlcomputer system 155, which can be integral with, connected to, orindependent from controller 180 (see FIG. 8). In particular, andreferring particularly to FIGS. 10 and 11, such an object is thereceiver aircraft 20 and more particularly a part AP thereof includingthe fuel receptacle 22, and the sensing volume 159 defines an outerenvelope limit 158 in which image data of part AP can be processed,inter alia, by control computer system 155 to provide control signals,for example steering commands, to the spatial control system 160 and/orthe force generating arrangement 190, for example via controller 180 tocontrol operation of the refueling device 100, in particular therelative spatial position and orientation of the refueling device 100with respect to the receiver aircraft 20, in particular the position andorientation of the boom member 130 and nozzle 135 with respect to thefuel receptacle 22, so that the nozzle 135 can be controllably broughtinto selective engagement with the fuel receptacle 22 in a safe andeffective manner. The manner of operation of the imaging system 150 andcontrol computer system 155 will be described in greater detail furtherherein.

In this example, the imaging system 150 comprises two pairs of flashladar units 151, also referred to interchangeably herein as FLADARunits, one pair on the trailing edge of each boss 186. Suitable FLADARunits can include, for example, a PMD [Vision]® CamCube 3.0, provided byPMD Technologies, Germany, and adapted for operating within therefueling unit and at the flight conditions thereof.

In operation the FLADAR units 151 illuminate the sensing volume 159 andany object therein, in particular part AP of the receiver aircraft 20and thereafter acquire suitable image data corresponding thereto whichis sent to control computer system 155 for processing to provide theaforesaid control signals for controlling the refueling device 100. Inparticular, by means of the FLADAR units 151, a 3D image of the areas APis reconstructed, and manipulated via a computer system to determine therelative position and orientation of the nozzle 135 with respect to thefuel receptacle 22.

The sensing volume 159 thus includes the engagement enabling position.

In alternative variations of this example and in other examples, theimaging system 150 can comprise any other suitable imaging system (forexample, but not limited to, systems providing 2D images and/orstereoscopic images and/or 3D images of (including reconstruction of 3Ddata corresponding to) the sensing volume 159, in particular but notlimited to images that are updated in real time, for example in the formof a video stream) that operate to provide suitable data to the controlcomputer system 155 to, in turn, enable selectively controlling therefueling device 100 to provide autonomous and/or manual engagement ofthe nozzle 135 to the fuel receptacle 22 of the receiver aircraft 20.

In alternative variations of this example, the imaging system 150 can bereplaced with any other suitable data acquisition system for providingthe aforesaid spatial data.

In yet other alternative variations of this example and in otherexamples, the refueling device 100 can omit the imaging system 150 andcan be actively controlled by an operator, for example, to control therelative spatial position and orientation of the refueling device 100with respect to the receiver aircraft 20, in particular the spatialposition and orientation of the boom member 130 and/or nozzle 135 withrespect to the fuel receptacle 22, so that the nozzle 135 can becontrollably brought into selective engagement with the fuel receptacle22 in a safe and effective manner, for example via direct visualtracking of the device by the operator. Alternatively, the refuelingdevice can be operated as a free flying refueling device towed at theend of hose 52, and the relative spatial position and orientation of therefueling device 100 with respect to the receiver aircraft 20 (inparticular the position and orientation of the boom member 130 andnozzle 135 with respect to the fuel receptacle 22, so that the nozzlecan be controllably brought into selective engagement with the fuelreceptacle 22 in a safe and effective manner) is achieved by maneuveringthe receiver aircraft only. In such a case, the spatial control system160 can optionally comprise a non-adjustable aerodynamic stabilitysystem that is configured for allowing the refueling device 100 to adopta particular, pre-set, desired angle θ while maintaining a zero pitchingmoment (and/or zero yawing moment and/or zero rolling moment), thisbeing the design angle θ_(des) as discussed above for example.

Optionally, a suitable air-driven generator can be provided in therefueling device 100 to provide electrical power thereto. Additionallyor alternatively, electrical power can be provided to the refuelingdevice 100 by the tanker aircraft 12.

In at least some alternative variations of the first example therefueling device can comprise an aerodynamic stabilizer arrangement,different from the spatial control system 160 or from the forcegenerating arrangement 190. For example, each one of the alternativeexample variations illustrated in FIGS. 13( c) and 13(d) comprises suchan aerodynamic stabilizer arrangement in the form of a respective droguestructure 180″ fixed to the aft portion of the body. Such a droguestructure 180″ can be utilized for generating a drag which in turninduces a tension to the hose 52, thereby aiding reduction or dampeningof vibrations or oscillations in the hoe 52 that can otherwise occur.Such a drogue structure can also be provided for other examples, forexample the first example illustrated in FIG. 3 or alternativevariations thereof.

In the example of FIGS. 16( a) to 16(d), the respective refueling device100E comprises an aerodynamic stabilizer arrangement in the form of adrogue structure 180E forwardly spaced from a forward end 114E of thefrustoconical body 110E of refueling device 100E by a length pipe 52E,which is flexible but can be articulated instead, and the body 110Ecomprises a spatial control system 160E comprising a selectivelycontrollable aerodynamic control system 170E, comprising a forward set172E of two swept back aerodynamic control surfaces 173E mounteddirectly to body 110E at a forward portion thereof, and an aft set 174Eof two aerodynamic control surfaces 175E directly mounted to the body110E at an aft portion thereof in “Vee” configuration, a deployableairbrake system 190E provided on the aft end of multi-segmentedtelescopic boom 130E, which comprises a nozzle 135E at the terminus 136Ethereof.

The in-flight refueling systems 50 including the first example of therefueling device 100 or at least some alternative variations thereof,can be operated in a number of different ways to provide selectiveengagement of the nozzle 135 with the fuel receptacle 22 of a receiveraircraft 20, and enable subsequent refueling of the receiver aircraft 20from the tanker aircraft 12 in flight, for example as disclosed herein.

Referring to FIGS. 17( a) to 17(d), a second example of the refuelingdevice, designated herein with reference numeral 200, comprises theelements and features of the first example and/or of at least somealternative variations thereof, mutatis mutandis, with some differences,as will become clearer herein, and the refueling device 200 isconfigured for use with an in-flight refueling system, for example atleast one of the in-flight refueling systems 50 illustrated FIGS. 1 and2.

For convenience, and referring to FIG. 17( a) for example, a roll axisR, a pitch axis P and a yaw axis Y can be conventionally defined withrespect to the refueling device 200. The roll axis R is parallel to orco-axial with the longitudinal axis 211 of the device 200; the pitchaxis P is generally in lateral and orthogonal relationship to the rollaxis R (i.e., parallel to the horizontal when the body is at a zero rollangle); and yaw axis Y is in orthogonal relationship to the roll axis Rthe pitch axis P (i.e., parallel to the vertical when the body is at azero pitch angle).

Refueling device 200 is affixed to the end 54 of hose 52 and comprisesbody 210 comprising a longitudinal axis 211, a fuel delivery lumen 220,and a substantially rigid boom member 230 in fluid communicationtherewith. The boom member 230 comprises a plurality of telescopicelements 232, defines a boom axis 231, and comprises a fuel deliverynozzle 235 at a terminus 236 of the boom member 230. The nozzle 235 isconfigured for reversibly engaging with the fuel receptacle 22 of areceiver aircraft 20, and thus can be similar to the nozzle 135 of thefirst example and as disclosed above, mutatis mutandis.

The boom member 230 is telescopically and pivotably mounted to body 210about axis C (generally parallel to the pitch axis P of the body 210),and is reversibly movable from a stowed position in which the telescopicelements 232 are retracted and nested in one another and the boom member230 is pivoted about axis C into a position accommodated in body 210(wherein optionally the boom axis 231 can be generally parallel tolongitudinal axis 211), to a deployed position illustrated in FIGS. 17(a) and 17(b). In the deployed position, the boom member 230 can be, bymeans of a controllable actuation mechanism (not shown), controllablyvariably extended in an aft direction from the aft end 212 of body 210,up to the fully extended position illustrated in FIGS. 17( a) and 17(b),and/or variably pivoted about pivot axis C in a downward direction toprovide a non-zero angular displacement, angle θ′, between boom axis 231and longitudinal axis 211. In this example, angle θ′ is in pitch, thoughin alternative variations of this example angle θ′ may also includeangular components in yaw and/or roll.

The body 210 optionally comprises a coupling 240 at forward end 214thereof, similar to the coupling 140 of the first example or alternativevariations thereof and as disclosed above, mutatis mutandis.

The refueling device 200 further comprises a spatial control system 260,configured for controlling a spatial disposition of the refueling device200 when towed aft of the tanker aircraft 12 via the hose 52. Inparticular, spatial control system 260 is configured for selectively andcontrollably providing a non-zero angular disposition, angle θ, betweenthe boom axis 231 and the forward direction A, and enables this angle θto be selectively maintained between the boom axis 231 and the forwarddirection A when the refueling device 200 is being towed by the tankeraircraft 12 via hose 52, similar to the corresponding feature of thefirst example or alternative variations thereof and as disclosed above,mutatis mutandis. Thus, in particular, angle θ is in pitch, i.e., abouta pitch axis P of the refueling device 200 and is defined on a planeincluding the roll axis R and the yaw axis Y of the refueling device200. Nevertheless, and depending on specific conditions during anyparticular refueling operation, angle θ can instead include an angulardisplacement component between the boom axis 231 and the forwarddirection A in yaw (i.e., about yaw axis Y) for example due to sideslipangle, and/or in roll (i.e. about roll axis R), in addition to anangular displacement component in pitch (i.e., about pitch axis P).

Thus, the spatial control system 260 is configured for controllablyflying the refueling device 200, and for providing stability to therefueling device 200, while tethered and towed via the hose 52, andwhile the boom axis 231 is at any desired pitch and/or yaw and/or rollangle corresponding to the aforesaid angle θ, and in particular, angle θis a design angle (angle θ_(des)) is within a particular angular rangewhich corresponds to the design relative angular position of the boommember 230 (and boom axis 231) with respect to the receiver aircraft 20similar to the corresponding feature of the first example or alternativevariations thereof and as disclosed above, mutatis mutandis.

In the second example, though, at least a part of angle θ, in particulara part of the design angle θ_(des) is provided by angle θ′, i.e., bypivoting the boom member 230 about axis C, depending on the magnitude ofangle φ, which is the relative angular disposition between thelongitudinal axis 211 and the forward direction A. The angle φ can bepositive (as illustrated in FIG. 17( b)), representing a positive angleof attack of body 210 with respect to forward direction A.Alternatively, angle φ can be negative, or zero.

In this example, the spatial control system 260 is configured forproviding a zero or near zero angle φ when the boom member 230 is in itsdeployed position pivoted at angle θ′, and comprises a selectivelycontrollable aerodynamic control system 270. The aerodynamic controlsystem 270 comprises a forward set 272 of aerodynamic control surfaces273 in the form of low aspect ratio wing members fixedly mounted to body210 at a forward portion thereof and having controllably movableailerons 271. The aerodynamic control system 270 further comprises anaft set 274 of aerodynamic control surfaces 275 mounted to the body 210at an aft portion thereof in “Vee” configuration. The spatial controlsystem 260 is also configured for providing the required pivoting angleθ′ so that angle θ′ together with angle φ provide the desired angle θbetween the boom axis 231 and the forward direction A in order tomaintain the required design angle θ_(des) between the boom axis 231 andthe longitudinal axis of the receiver aircraft 20. Thus, angle θ (whichcan have an angular component in yaw and/or in pitch and/or in roll)compensates for any off-nominal pitch of the receiver aircraft 20 (forexample if the receiver aircraft 20 is traveling along direction A at anon-zero angle of attack) and/or for any off-nominal roll of thereceiver aircraft 20 (for example if the receiver aircraft 20 istraveling along direction A at a non-zero roll angle) and/or for anyoff-nominal yaw of the receiver aircraft 20 (for example if the receiveraircraft 20 is traveling along direction A at a non-zero sideslip angle)to ensure that the actual angular disposition between the boom axis 231and the receiver aircraft longitudinal axis is maintained at designangle θ_(des) even as the relative spatial orientation between thereceiver aircraft 20 and the forward direction A changes.

In other variations of the example and in other examples, the spatialcontrol system 260 can be similar to the corresponding feature of thefirst example or alternative variations thereof and as disclosed above,mutatis mutandis.

The refueling device 200 can optionally further comprise a forcegenerating arrangement (not shown), similar to the corresponding featureof the first example or alternative variations thereof and as disclosedabove, mutatis mutandis.

The refueling device 200 can optionally further comprise a suitablespatial data acquisition system including an imaging system (not shown),similar to the corresponding feature of the first example or alternativevariations thereof and as disclosed above, mutatis mutandis, or can omitsuch an imaging system and can be actively controlled by an operator,for example, similar to the corresponding feature of the first exampleor alternative variations thereof and as disclosed above, mutatismutandis.

The in-flight refueling systems 50 including the second example of therefueling device 200, and at least some alternative variations thereof,can also be operated in a number of different ways to provide selectiveengagement of the nozzle 235 with the fuel receptacle 22 of a receiveraircraft 20, and enable subsequent refueling of the receiver aircraft 20from the tanker aircraft 12 in flight.

There is now provided a description of certain examples of systems ofcontrolling in-flight refueling.

Reference is now made to FIG. 18, which is a block diagram schematicallyillustrating a system for controlling in-flight refueling, according tocertain examples of the presently disclosed subject matter. The system1805 comprises at least one processing unit 1801. The processing unit1801 can be a microprocessor, a microcontroller or any other computingdevice or module, including distributed and/or multiple processingunits, which are adapted to independently or cooperatively process datafor controlling relevant system 1805 components and for enablingoperations related to system 1805 components.

In some cases, the processing unit 1801 can be the control computersystem 155, or part thereof. In some cases, the processing unit can bethe controller 180. Alternatively, the processing unit 1801 can be aseparate component.

In some cases, the processing unit 1801 can be located on-board therefueling device 100, or on-board the receiver aircraft 20, or on-boardthe tanker aircraft 12. In some cases, more than one processing unit canbe used and the plurality of processors can be cooperatively operated.

In some cases, the system 1805 can be distributed between the refuelingdevice 100 and/or the receiver aircraft 20, and/or the tanker aircraft12 and/or any other location, including remote locations. Thecommunication between the various components of the system 1805 can berealized by any communication components, protocols and modules, and canbe wired or wireless.

The system 1805 further comprises a sensor control module 1810.According to some examples of the presently disclosed subject matter,the sensor control module 1810 can be configured to utilize at least onesensor 1890 (possibly according to instructions from the processing unit1801) as part of the operation of and control over the refuelingprocess.

The sensor control module 1810 can be operatively connected to at leastone sensor 1890 and can be configured to control the operation of thesensor 1890. The sensor 1890 can be a suitable data acquisition system,for example, any image acquisition means such as a camera (e.g. adigital still camera, a digital video camera, a Flash LADAR camera,etc.). Alternatively, the sensor 1890 can be a radar, a laser array,electro-acoustic sensors, etc. In some cases, sensor 1890 can beconfigured inter alia for providing data of any object coming within afield of regard (FOR) aft of the refueling device 100 (and/or the tankeraircraft 12). In some cases, the sensor 1890 can be the imaging system150 detailed herein. In some cases, imaging system 150 can be configuredinter alia for providing imaging data of any object coming within afield of regard (FOR) aft of the refueling device 100 (and/or the tankeraircraft 12). The sensor control module 1810 is configured to operatesensor 1890 in order to acquire data that enables, inter alia, repeateddetermination of spatial data such as the spatial disposition of thereceiver aircraft 20 with respect to an engagement area related theretoand/or determination of the spatial dispositions of the refueling device100 with respect to an engagement enabling position, etc. as furtherdetailed herein, inter alia with respect to FIGS. 22 and 23.

The system 1805 can further comprise a maneuvering instructions module1820, a steering control module 1830, a safety module 1840, and anengagement/disengagement control module 1850.

Maneuvering instructions module 1820 can be configured to calculatemaneuvering instructions for enabling positioning of the receiveraircraft 20 within an engagement area related thereto, and for providingthe calculated maneuvering instructions to a pilot of the receiveraircraft 20, as further detailed, inter alia with respect to FIG. 20.

Steering control module 1830 can be configured to calculate and providesteering commands to the refueling device 100 for steering the refuelingdevice 100 to an engagement enabling position, as further detailedherein, inter alia with respect to FIG. 21.

Safety module 1840 can be configured to monitor hazardous situations inthe refueling process, as further detailed herein, inter alia withrespect to FIG. 19. The hazardous situations can be defined by a set ofthresholds and/or parameters and respective safety conditions. Forexample, safety module 1840 can be configured to monitor that therefueling device 100 does not approach the receiver aircraft 20 (or viceversa) in an unsafe manner, and/or that the refueling device 100 doesnot approach the tanker aircraft 12 (or vice versa) in an unsafe manner,etc.

Engagement/disengagement control module 1850 can be configured toprovide an engagement command to the refueling device 100 for causingthe refueling device 100 to engage with the fuel receptacle 22 of thereceiver aircraft 20 for performing refueling, and to provide a commandto the refueling device 100 to disengage from the fuel receptacle 22 ofreceiver aircraft 20, as further detailed herein. According to examplesof the presently disclosed subject matter, engagement/disengagementcontrol module 1850 can be responsive to an indication that the receiveraircraft 20 is positioned in an engagement enabling position. Theengagement enabling position, in some cases, can depend on a spatialdisposition of the refueling device 100 with respect to the receiveraircraft 20, as further detailed herein.

The system 1805 can further comprise a configuration data repository1860 (hereinafter: “Configuration DR”) and a reference data repository1870 (hereinafter: “Reference DR”). Configuration DR 1860 comprises dataindicative of various predefined configurations that are used in therefueling process. According to examples of the presently disclosedsubject matter, the configuration DR 1860 can include configuration datarelated to an engagement area and an engagement enabling position.Further, by way of example, the configuration data related to theengagement area and the engagement enabling position can be used todetermine the engagement area and/or the engagement enabling position ina given scenario (and for a given set of parameters). Additional datawith respect to the configuration data will be provided herein, interalia with respect to FIGS. 22 and 23. Reference DR 1870 comprisesreference data to be used, inter alia, for determining (it is to benoted that in some cases such determination is made, for example,repeatedly) the receiver aircraft's 20 spatial disposition with respectto the engagement area related thereto and the refueling device's 100spatial disposition with respect to the engagement enabling position,etc. According to some examples, the reference data can be used incombination with dynamic data acquired by the sensor 1890 for enablingevaluation of the sensor's 1890 data. Further explanations regarding thereference data are provided herein, inter alia with respect to FIGS. 22and 23. It is to be noted that in some cases, Reference DR 1870 can alsobe used by the safety module 1840 for determining hazardous situations.

It is to be noted that according to some examples of the presentlydisclosed subject matter, some or all of the Configuration DR 1860, theReference DR 1870, the sensor control module 1810, the maneuveringinstructions module 1820, the steering control module 1830, the safetymodule 1840, and the engagement/disengagement control module 1850 can becombined and provided as a single system/module, or, by way of example,at least one of them can be realized in a form of two or moresystems/modules, each of which can in some cases be distributed overmore than one location.

The system can still further comprise an interface 1880 for enabling oneor more components of the system 1805 to operate in cooperation withauxiliary units, devices, systems or modules. For example, the interface1880 can implement various protocols, software languages, drive signals,etc. Further, by way of example, the interface 1880 can be used tooperate certain auxiliary units, devices, systems or modules on boardone or more of the refueling device 100, the receiver aircraft 20 or thetanker aircraft 12.

According to another aspect of the presently disclosed subject matter,there are provided methods for in-flight refueling of aircraft. Whilesuch methods can be applied to the systems and devices for in-flightrefueling of aircraft according to another aspect of the presentlydisclosed subject matter, and as disclosed herein, for example, themethods can also be applied to other suitable systems and devices forin-flight refueling of aircraft, mutatis mutandis.

According to the second aspect of the presently disclosed subjectmatter, there are at least three alternative operation modes forin-flight refueling of aircraft:

Operation Mode I—in which a refueling device is automatically (and insome cases autonomously) flown to engagement with the receiver aircraftfuel receptacle.

Operation Mode II—in which an operator in the tanker aircraft orelsewhere (via suitable communications link—for example satellite link,another aircraft including the receiver aircraft, ground control, and soon) controls flying of a refueling device while towed behind the tankeraircraft to engagement with the receiver aircraft fuel receptacle.

Operation Mode III—in which the refueling device is not flown orcontrolled per se, but instead attains a stable configuration with theboom member at the required inclination angle with respect to theforward direction, and the receiver aircraft maneuvers to a positionwhere it can engage the nozzle to the receiver aircraft fuel receptacle.

Examples of these operation modes will now be described in greaterdetail.

Operation Mode I

In this operation mode, once the tanker aircraft 12 and receiveraircraft 20 are in close proximity and flying in formation, with thereceiver aircraft 20 at a position behind the tanker aircraft 12, therefueling device 100 automatically (and in some cases, autonomously)flies into engagement with the fuel receptacle 22 of the receiveraircraft 20.

Turning to FIG. 19 there is provided a flowchart illustrating a sequenceof operations carried out for enabling performance of in-flightrefueling, according to certain examples of the presently disclosedsubject matter, in particular relating to the example of a system forcontrolling in-flight refueling, as illustrated in FIG. 18. The sequenceof operations begins with performance of an engagement sequence 1905,comprising 3 blocks: 1910, 1920 and 1930.

Turning at first to block 1910, in some cases, maneuvering instructionsmodule 1820 is configured to calculate and provide maneuveringinstructions for enabling positioning the receiver aircraft 20, and morespecifically a fuel receptacle 22 thereof, within an engagement arearelated to the receiver aircraft 20 (as in cases where more than onereceiver aircraft 20 exists, each receiver aircraft 20 can be associatedwith a different engagement area) (block 1910), as further detailedherein with respect to FIGS. 20 and 22. Inter alia, some examples ofmethods that can be used for providing the maneuvering instructions tothe pilot of the receiver aircraft 20 are also provided herein.

It is to be noted that such maneuvering instructions can be required insome cases, where the pilot of the receiver aircraft 20 has no line ofsight to the refueling device 100 during all or part of the refuelingprocess, inter alia in light of the receiver aircraft 20 fuel receptacle22 position. Thus, there can be a need to provide the pilot of thereceiver aircraft 20 with maneuvering instructions, as further detailedherein.

As mentioned above, according to examples of the presently disclosedsubject matter, the refueling process can include providing maneuveringinstructions for positioning the receiver aircraft 20 within anengagement area related thereto. The engagement area is a virtual volumein which the refueling device 100 can be maneuvered in order to engagewith the fuel receptacle 22 of the receiver aircraft 20. According tosome examples of the presently disclosed subject matter, the engagementarea can be defined by various specifications that depend on severalparameters. According to one example, the parameters are associated withmaneuvering capabilities of the refueling device 100. Such maneuveringcapabilities can be defined, for example, by the range and types ofmotion that can be achieved by utilizing the spatial control system 160and/or the force generating arrangement 190, etc.

According to certain examples of the presently disclosed subject matter,the parameters defining the engagement area can further include, interalia, the length of the hose 52, the flight speed, the flight altitude,weather conditions, the fuel pressure within the hose 52, the locationof the fuel receptacle 22 of the receiver aircraft 20, etc. In somecases, the engagement area can be substantially in the shape of a cube,a sphere, or any other shape with a certain volume. The variousengagement area specifications can be stored, for example, onconfiguration DR 1860. For example, the engagement area specificationscan include a set of spatial dispositions between the refueling device100 and the receiver aircraft 20 or any other volumetric specification.According to further examples of the presently disclosed subject matter,the engagement area specifications can be used in combination withreference data for enabling the refueling device 100, based on dynamicdata acquired by the sensor 1890, to identify when the receiver aircraft20 is within a position that meets the engagement area specification. Inthis case, correlations can be computed between the data acquired by thesensor 1890 and the reference data, in order to determine if and whenthe receiver aircraft 20 is within the engagement area.

Before moving on to describe FIG. 19, and for the purpose of providing avisual illustration of an exemplary engagement area, attention is drawnto FIG. 24, showing an illustration of one example of a receiveraircraft positioned outside a virtual engagement area, according tocertain examples of the presently disclosed subject matter. Theengagement area 2410 in the illustrated example is a virtualpre-determined volume, shaped substantially like a cube, in which therefueling device 100 can navigate until engaging with the fuelreceptacle 22 of the receiver aircraft 20, as detailed herein. Althoughin this example the virtual engagement area is shaped substantially likea cube, the virtual engagement area can have any other shape with acertain volume. The virtual engagement area can be defined by a set ofparameters that correspond to a volumetric shape. It can be furtherappreciated that in the illustrated example, the receiver aircraft 20 isnot positioned within the engagement area 2410. The illustration of FIG.24 is provided for clarity of explanation only and is by no meansbinding.

Returning to FIG. 19, in some cases, the engagement area specificationscan be defined using, inter alia, a parameter denoting a position of thecenter of such an engagement area, or any other point within theengagement area, and a set of offset vectors, collectively representinga volume. In some cases, the center (or any other point of reference) ofthe engagement area can be determined in accordance with one or more ofthe following parameters: the length of the hose 52 in a deployedposition, a given pitch angle between the boom axis 131 and the forwarddirection A, a given yaw angle between the boom axis 131 and the forwarddirection A and a given fuel pressure within the hose 52, etc. One ormore of the parameters which are used to determine the center (or anyother point of reference) of the engagement area can vary during flightand/or during the engagement sequence 1905 and the system 1805 canmeasure the relevant parameters dynamically for determining the center(or any other point of reference) of the engagement area.

In some cases, the point of reference for the engagement area can bepositioned in a position from which utilization of the force generatingarrangement 190 enables the nozzle 135 to engage with the fuelreceptacle 22 of the receiver aircraft 20 and the engagement area isdefined with reference to this point. In some examples, this point ofreference is defined in the system as an engagement enabling position,and can also be used by an engagement/disengagement control module 1850,for controlling engagement and of the nozzle 135 with the fuelreceptacle 22 of the receiver aircraft 20. It will be appreciated thatthis point can also depend, inter alia, on the parameters describedherein, and in some cases, is dynamically calculated according to therelevant parameters during the engagement sequence 1905.

According to some examples of the presently disclosed subject matter,the engagement enabling position can be characterized by the boom member130 being in a predetermined maximal spaced and spatial relationshipwith respect to the fuel receptacle 22 of the receiver aircraft 20.Throughout the description and the claims, reference is madeinterchangeably to the terms spatial relationship and spatialdisposition. The terms spatial relationship and spatial disposition orthe like can relate to spatial distances, spatial angles (includingorientations), or any other spatial reference that is used forcharacterizing a spatial relationship between two objects, e.g. betweenany two of the following: the tanker aircraft 12, the receiver aircraft20 (and a fuel receptacle 22 thereof) and the refueling device 100. Insome cases the spatial relationship can include aligning the boom axis131 of the boom member 130 in an engagement enabling orientation.

In some cases, the maximal spaced relationship between the boom member130 of the refueling device 100 and the fuel receptacle 22 of thereceiver aircraft 20 at the engagement enabling position can depend onvarious parameters, such as: the hose 52 length and flexibility, theflight speed, the flight altitude, the characteristics of the forcegenerating arrangement 190, etc., and in such cases, the maximal spacecan be calculated as necessary, inter alia dynamically during therefueling process, based on current values of the respective parameters.For example, it can be appreciated that the less flexible the hose 52,the maximal space between the boom member 130 of the refueling device100 and the fuel receptacle 22 of the receiver aircraft 20 at theengagement enabling position is reduced. In some cases, the maximalspace between the boom member 130 of the refueling device 100 and thefuel receptacle 22 of the receiver aircraft 20 at the engagementenabling position can be defined by the movement range of the boommember 130 in the direction of the fuel receptacle 22 of the receiveraircraft 20.

In some cases, the spatial relationship between the boom member 130 ofthe refueling device 100 and the fuel receptacle 22 of the receiveraircraft 20 at the engagement enabling position can also depend onvarious parameters, such as the characteristics of the fuel receptacle22 of the receiver aircraft 20, etc.

According to examples of the presently disclosed subject matter thespatial relationship with which the engagement enabling position isassociated can also include an angle parameter. In this regard, it canbe appreciated that in case the fuel receptacle 22 of the receiveraircraft 20 has an entrance angle, the boom axis 131 of the boom member130 should be in a spatial disposition that enables the nozzle 135 toengage therewith (e.g. the boom axis 131 needs to be aligned with a fuelreceptacle 22 of the receiver aircraft 20). It has been explained hereinthat spatial control system 160 can, in accordance with certainexamples, be configured for selectively and controllably providing anon-zero angular disposition, angle θ, between the boom axis 131 and theforward direction A, that enables this angle θ to be selectivelymaintained between the boom axis 131 and the forward direction A atleast for a part of the time when the refueling device 100 is beingtowed by the tanker aircraft 12 via hose 52, and in particular duringthe engagement operation of the fuel device 100 to the receiver aircraft20 and during refueling thereof. It is to be noted that such angle θ canbe predetermined. In some cases the angle θ can be stored in theconfiguration DR 1860.

In some examples, it is to be noted that the engagement enablingposition is not necessarily a specific x, y, z coordinate, as, undercertain conditions, the exact coordinates of the point of reference forthe engagement area can vary, or some tolerance can be accepted (forexample using tolerance ranges). In addition, there can be more than oneengagement enabling position that meets the conditions detailed herein,each of which is an engagement enabling position.

Before moving on to describe FIG. 19, and for the purpose of providing avisual illustration of an exemplary engagement enabling position,attention is drawn to FIG. 26 and FIG. 27. Reverting to FIG. 26, thereis shown an illustration of an example of a refueling device not in anengagement enabling position, according to certain examples of thepresently disclosed subject matter. It can be appreciated that thereceiver aircraft 100, and more particularly a fuel receptacle 22thereof, is positioned within the engagement area 2410, however, therefueling device 100 is not positioned in an engagement enablingposition. In this example, as illustrated in FIG. 26, it can beappreciated that the refueling device 100 is not aligned with the fuelreceptacle 22 of the receiver aircraft 100. The illustration of FIG. 26is provided for clarity of explanation only and is by no means binding.Reverting to FIG. 27, there is shown an illustration of an example of arefueling device positioned in an engagement enabling position,according to certain examples of the presently disclosed subject matter.It can be appreciated that the refueling device 100 is positioned in anengagement enabling position that can enable engagement with the fuelreceptacle 22 of the receiver aircraft 100. The illustration of FIG. 27is provided for clarity of explanation only and is by no means binding.

Returning to FIG. 19, in some cases, maneuvering instructions module1820 can be configured to provide the maneuvering instructions forenabling positioning of the receiver aircraft 20 within an engagementarea, for example by utilizing a signaling system. Such signaling systemcan be mounted, for example, on the tanker aircraft 12, at any locationvisible to the receiver aircraft 20 pilot. In some cases, the signalingsystem can provide the receiver aircraft 20 pilot with maneuveringinstructions on three axes: forward-backward, left-right and up-down,thus enabling it to maneuver the receiver aircraft 20 to the engagementarea 2410. In some cases the signaling system can be a light directingsystem. Alternatively or additionally, the maneuvering instructions canbe provided to by using voice commands (e.g. by utilizing speakers,pilot headset, etc.) or by any other means known per se. In some cases,maneuvering instructions module 1820 can be configured to communicatethe maneuvering instructions to an auto pilot system of the receiveraircraft 20, if such system exists, for causing the auto pilot system tomaneuver the receiver aircraft 20 accordingly.

Before moving on to describe FIG. 19, and for the purpose of providing avisual illustration of an exemplary engagement area, attention is drawnto FIG. 25, showing an illustration of an example of a receiver aircraftpositioned inside a virtual engagement area, according to certainexamples of the presently disclosed subject matter. It can be noted thatthe receiver aircraft 20, and more particularly the fuel receptacle 22thereof, are positioned within the engagement area 2410. Also in thisillustration the engagement area 2410 is a virtual pre-determinedvolume, shaped substantially like a cube, in which the refueling device100 can navigate until arriving at an engagement enabling position (inwhich the boom member 130 is in a predetermined maximal spaced andspatial relationship with respect to the fuel receptacle 22 of thereceiver aircraft 20) and engaging with the fuel receptacle 22 of thereceiver aircraft 20, as detailed herein. Although also in this examplethe virtual engagement area is shaped substantially like a cube, thevirtual engagement area can have any other shape with a certain volume.It can be noted that the illustration further illustrates an example ofa signaling system 2420 mounted on tanker aircraft 12. It can beappreciated that such a signaling system can be used by maneuveringinstructions module 1820 for providing maneuvering instructions to thepilot of the receiver aircraft 20. It is to be noted that alternativeand/or additional signaling systems can be used. The illustration ofFIG. 25 is provided for clarity of explanation only and is by no meansbinding.

Bearing all this in mind, and returning to FIG. 19, it is to be notedthat block 1910 can be performed repeatedly (e.g. every pre-determinedperiod) or continuously, at least until the nozzle 135 is engaged withthe fuel receptacle 22 of the receiver aircraft 20, as further detailedherein. Thus, while the receiver aircraft 20 is not positioned withinthe engagement area, maneuvering instructions module 1820 provides thepilot of the receiver aircraft 20 (and, in some cases, an auto pilotsystem that controls the maneuvering of the receiver aircraft 20) withmaneuvering instructions for positioning the receiver aircraft 20 withinan engagement area.

Although the process above (referring to block 1910) was described withrespect to maneuvering of the receiver aircraft 20, it is to be notedthat in some cases, in addition or as an alternative to maneuvering ofthe receiver aircraft 20 for approaching the refueling device 100, thetanker aircraft 12 can approach the receiver aircraft 20, thus bringingthe refueling device 100 in the direction of the receiver aircraft 20.In such cases, the maneuvering instructions can be additionally oralternatively provided to the pilot of the tanker aircraft 12 mutatismutandis.

It is to be further noted that the process relating to block 1910 can insome cases be an independent process, and in other cases it can beperformed as part of a sequence of processes, such as engagementsequence 1905.

Turning now to block 1920 in FIG. 19, in some cases, once an engagementarea specification condition is met (e.g. it is determined that thereceiver aircraft 20 is positioned within the engagement area), steeringcontrol module 1830 can be configured to provide commands for causingthe steering of the refueling device 100 to an engagement enablingposition, in which the boom member 130 is in a predetermined maximalspaced and spatial relationship with respect to the fuel receptacle 22of the receiver aircraft 20 (block 1920), as further detailed herein,inter alia with respect to FIGS. 21 and 23.

In some cases, the steering commands module 1830 can be operativelyconnected to the spatial control system 160 and/or to the forcegenerating arrangement 190 of the refueling device 100. In such cases,the steering commands module 1830 can provide steering commands forcontrolling the spatial control system 160 and/or to the forcegenerating arrangement 190 and thus enabling steering the refuelingdevice 100 to an engagement enabling position, in which the boom member130 is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20.

In some cases, the steering commands can be based, inter alia, oncharacteristics of the spatial control system 160. Such characteristicscan be, for example, operation parameters of reaction control thrustersassociated with the refueling device and capable of steering therefueling device 100 and/or operation parameters of aero-dynamic controlsurfaces of the refueling device 100.

In some cases, based on the steering commands from the steering commandsmodule 1830, the refueling device 100 can be adapted to steerautomatically. In particular, in some cases, using the commands,autonomous steering of the refueling device 100 can be achieved (e.g.when all the necessary components are fitted within the refueling device100).

Thus, in accordance with some examples of the presently disclosedsubject matter, there can be provided a refueling device 100 which canbring itself automatically, and in some cases (when all the necessarycomponents are fitted within the refueling device 100) autonomously,into fluid communication with the fuel receptacle 22 of the receiveraircraft 20. In further examples, there can be provided a refuelingdevice which can automatically, and in some cases (when all thenecessary components are fitted within the refueling device 100)autonomously, align its boom axis 131 with a fuel receptacle 22 of thereceiver aircraft 20, and move the boom member 130 in a predeterminedtrajectory towards the receiver aircraft 20 and thus enable therefueling device 100 to automatically bring itself into engagement withthe fuel receptacle 22 of the receiver aircraft 20.

It is to be noted that block 1920 can be performed repeatedly (e.g.every pre-determined period) or continuously. For example, block 1920can be performed until engagement of the nozzle 135 to the fuelreceptacle 22 of the receiver aircraft 20, as further detailed herein,and in some cases even after such engagement. While the refueling device100 is not positioned within an engagement enabling position, steeringcontrol module 1830 provides the refueling device 100 with steeringcommands for maneuvering the refueling device 100 to the engagementenabling position, in which the boom member 130 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20.

It is to be further noted that the process relating to block 1920 can insome cases be an independent process, and in other cases it can beperformed as part of a sequence of processes, such as engagementsequence 1905.

Attention is now drawn to block 1930 in FIG. 19. In some cases, once thereceiver aircraft 20 is positioned within the engagement area and therefueling device 100 is positioned in an engagement enabling position(in which the boom member 130 is in a predetermined maximal spaced andspatial relationship with respect to the fuel receptacle 22 of thereceiver aircraft 20), the engagement/disengagement control module 1850can be configured to provide the refueling device 100 with an engagementcommand for causing the refueling device 100 to engage to the fuelreceptacle 22 of the receiver aircraft 20 for enabling refueling of thereceiver aircraft 20 (block 1930). It is to be noted that at theengagement enabling position the nozzle 135 is properly aligned with thefuel receptacle 22 (the boom member 130 and boom axis 131 being at thedesign angle θ_(des) to the forward direction A) and sufficiently closethereto, i.e., at a predetermined spacing from the receiver aircraft,said boom axis being aligned in an engagement enabling orientation atsaid spaced position.

In some cases, the engagement command can cause activation of the forcegenerating arrangement 190, e.g., by deploying the air brakes 195, 196,thus generating a force along boom axis 131 that effectively pushes thenozzle 135 into engagement with the fuel receptacle 22 of the receiveraircraft 20. Such force can cause the boom member 130 to move in apredetermined trajectory towards the receiver aircraft 20 for enablingengagement between the nozzle 135 and the fuel receptacle 22 of thereceiver aircraft 20 (e.g. for enabling fuel communicationtherebetween). In some cases, prior to deploying the air brakes 195,196, the boom member 130 can be extended, for example until reaching apre-determined space from the fuel receptacle 22 of the receiveraircraft 20. In some cases, the engagement command can cause extensionof the boom member 130 until connection with the fuel receptacle 22 ofthe receiver aircraft 20, with no use of any air brakes mechanism. Inother words, once the refueling device 100 is at the aforesaidengagement enabling orientation and spaced position, the boom member issubsequently moved along said boom axis towards the receiver aircraftfor enabling fuel communication therebetween. Movement of the boommember can be effected in one of two ways, or combination thereof: therefueling device 100 remains in the spaced position, and the boom member130 is extended telescopically; the boom member 130 can be in theretracted or extended position, and the refueling device 100 is bodilymoved towards the receiver aircraft for enabling fuel communicationtherebetween.

In accordance with some examples of the presently disclosed subjectmatter, there can be provided a refueling device 100 which can bringitself automatically, and in some cases (when all the necessarycomponents are fitted within the refueling device 100) autonomously,into fluid communication with the fuel receptacle 22 of the receiveraircraft 20. In further examples, there can be provided a refuelingdevice 100 which can automatically, and in some cases (when all thenecessary components are fitted within the refueling device 100)autonomously, engage the nozzle 135 with the fuel receptacle 22 of thereceiver aircraft 20.

In some cases, prior to providing the refueling device 100 with anengagement command, maneuvering instructions module 1820 can beconfigured to cause a signaling system to provide the pilot of thereceiver aircraft 20 with a notification indicating that the refuelingdevice 100 is about to engage to the fuel receptacle 22, thus requiringthe pilot of the receiver aircraft 20 to stabilize it.

It is to be further noted that the process relating to block 1930 can insome cases be an independent process, and in other cases it can beperformed as part of a sequence of processes, such as engagementsequence 1905.

Attention is now drawn to Block 1940 in FIG. 19. In some cases,following engagement sequence 1905, the system 1805 can be configured toprovide a command to the refueling device 100 to perform refueling ofthe receiver aircraft 20 by pumping fuel to the receiver aircraft 20from the tanker aircraft 12 (block 1940). In some cases, at any timefollowing engagement sequence 1905, the system 1805 can be furtherconfigured to deactivate the force generating arrangement 190, e.g. byretracting the air brakes 195, 196.

In one example, the command to deactivate the force generatingarrangement 190 and the refueling command can be issued by theengagement/disengagement module 1850. Further by way of example,engagement/disengagement module 1850 can be configured to provide adeactivation command when an indication is received that the refuelingdevice 100 is engaged with the receiver aircraft 20. Further by way ofexample, the refueling command can be issued for example when anengagement indication is issued.

Attention is now drawn to Block 1950 in FIG. 19. theengagement/disengagement control module 1850 can be further configuredto provide the refueling device 100 with a disengagement command forcausing the refueling device 100 to disengage from the fuel receptacle22 of the receiver aircraft 20 in response to receiving an indicationthat the fuel level in the fuel tank of the receiver aircraft 20 reacheda desired level or when an indication of a hazard is issued (block1950).

In some cases, prior to providing the refueling device 100 with adisengagement command, maneuvering instructions module 1820 can beconfigured to cause the signaling system to provide the pilot of thereceiver aircraft 20 with a notification indicating that the refuelingis done, and in some cases instruct the pilot of the receiver aircraft20 to perform a maneuver in order to fly away from the refueling device100.

It is to be noted that throughout the refueling process, safety module1840 can monitor certain parameters, for example parameters that relateto the spatial dispositions between any two or more of the following:the receiver aircraft 20, the refueling device 100 and the tankeraircraft 12, as well as other parameters including the angles, etc.,possibly in comparison to predefined reference thresholds or parametersor ranges, to identify possible hazardous situations. Such hazardoussituations can include, inter alia, a dangerous approach of the receiveraircraft 20 to the refueling device 100 or to the tanker aircraft 12, adangerous movement of the receiver aircraft 20, and/or the refuelingdevice 100 and/or the tanker aircraft 12, including such movement whenthe refueling device 100 is engaged to the receiver aircraft 20, etc. Itis to be noted that such hazardous situations can be caused for exampledue to a human error, environmental conditions (weather, wind, etc.), aswell as other causes. It is to be further noted that for monitoring suchhazardous situations, safety module 1840 can be configured to utilize,inter alia, sensor control module 1810 for sensing the spatialdispositions of the receiver aircraft 20, and/or the refueling device100 and/or the tanker aircraft 12.

In some cases, when safety module 1840 identifies a hazardous situation(e.g. a safety condition is met or, in some cases, is not met), it canbe configured, inter alia, to instruct steering control module 1830 toprovide steering instructions for causing the refueling device 100 tosteer away from the receiver aircraft 20, and/or to provide anindication to the pilot of the receiver aircraft 20 that a hazardoussituation has been identified, thus enabling the pilot to maneuver thereceiver aircraft 20 away from danger, etc. It is to be noted that incase the hazardous situation is identified after the refueling device100 engaged with the receiver aircraft 20, safety module 1840 can befurther configured to instruct engagement/disengagement module 1850 tocause the refueling device 100 to disengage from the receiver aircraft20 prior to performing the steering as detailed herein.

It is to be noted that in some cases, when the receiver aircraft 20 ispositioned within the engagement area, or at an earlier stage, therefueling device 100 can be deployed to an initial trail position. Suchinitial trail position can be defined in terms of a spatial dispositionwith respect to the tanker aircraft 12 and can be characterized, interalia, by one or more of the following:

-   -   A required deployment length of the hose 52 (that in some cases        can depend, inter alia, on the flight speed, the flight        altitude, the receiver aircraft 20 type, the engagement area        specification; etc., whereas in other cases it can be for        example pre-determined);    -   A required pitch angle between the boom axis 131 and the forward        direction A is maintained;    -   A required yaw angle between the boom axis 131 and the forward        direction A is maintained.

In some cases, the steering control module 1830 can be configured tomonitor the spatial disposition of the refueling device 100 with respectto the tanker aircraft 12 and validate that the refueling device 100 ispositioned in the initial trail position with respect to the tankeraircraft 12. For that purpose, steering control module 1830 can utilize,for example, sensor control module 1810 for repeatedly, and in somecases in real time (for example in the form of a video stream) acquiringan image of the area in which the refueling device 100 is expected to bepositioned when in the initial trail position. The image can be acquiredby a sensor 1890 that can be mounted, for example, on the tankeraircraft 12 in a position that enables it to acquire images of the areain which the refueling device 100 is expected to be positioned when inthe initial trail position. Such camera position can be, for example, onthe tanker aircraft 12 wing, tail, etc. Utilization of such an image canenable determination of the refueling device's 100 spatial dispositionwith respect to the tanker aircraft 12 (it is to be noted that in somecases such determination is made, for example, repeatedly). For example,the acquired image can be compared with a pre-stored image (e.g. storedon reference data repository 1870) of the refueling device 100,illustrating a desired spatial disposition with respect to the tankeraircraft 12, thus enabling determination of the relative spatialdisposition of the refueling device 100 with respect to the tankeraircraft 12 (it is to be noted that in some cases such determination ismade, for example, repeatedly). Such desired spatial disposition can, insome cases, depend on various factors, such as, inter alia, the flightspeed, the flight altitude, the refueling device 100 weight, etc. It canbe appreciated that pre-stored images of different spatial dispositionsof the refueling device 100 with respect to the tanker aircraft 12 canbe stored in reference DR 1870 and a set of parameters, inter alia,flight speed, flight altitude, refueling device 100 weight, etc., can bespecified in association with one or more of the pre-stored images.

According to examples of the presently disclosed subject matter, for agiven set of parameters, steering control module 1830 can determinewhich image is to be used as a reference image. For example, thesteering control module 1830 can receive a set of measurements which arecorrelated with the parameters associated with the images and cancompare the current measurements to the various sets of parameters andidentify which set is, for example, most closely correlated with themeasurements and the steering control module 1830 can select the imagewith which the parameters are associated as the reference image.Following the selection of the reference image, the steering controlmodule 1830 can repeatedly (e.g. every pre-determined period), orcontinuously, compare images obtained by the sensor 1890 during therefueling process to the selected reference image, and calculate thespatial disposition of the refueling device 100 with respect to theinitial trail position.

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the refueling device 100 withrespect to the tanker aircraft 12, an appropriate 3-D model can beselected (for example according to the type of the receiver aircraft 20)and the 3-D model can be adapted using current measurements (e.g.obtained by the sensor 1890) and respective parameters of the 3-D model.

According to other examples of the presently disclosed subject matter,steering control module 1830 can search among the different pre storedreference images for an image which most closely correlates with acurrent image and can determine the spatial disposition using thepre-stored parameters associated with the selected image.

It is to be noted that various other methods and techniques can be usedin order to determine the refueling device's 100 spatial dispositionwith respect to the tanker aircraft 12 (it is to be noted that in somecases such determination is made, for example, repeatedly).

It is to be noted that, with reference to FIG. 19, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also noted that whilst the flow diagrams are described alsowith reference to the system elements that realizes them, this is by nomeans binding, and the blocks can be performed by elements other thanthose described herein.

Turning to FIG. 20, there is shown a flowchart illustrating a sequenceof operations carried out for providing maneuvering commands forpositioning a receiver aircraft within an engagement area relatedthereto, according to certain examples of the presently disclosedsubject matter. Maneuvering instructions module 1820 can be configuredto determine (it is to be noted that in some cases, as indicated herein,such determination is made, for example, repeatedly) the receiveraircraft's 20 spatial disposition with respect to the engagement arearelated thereto (block 2005), as further detailed with respect to FIG.22.

Following determination of the receiver aircraft's 20 spatialdisposition with respect to the engagement area related thereto,maneuvering instructions module 1820 can be configured to check if thereceiver aircraft 20 is positioned within the engagement area (block2010), based for example on current measurements from sensor/s 1890 asdescribed herein. In some examples, in case the receiver aircraft 20 ispositioned within the engagement area, and until the refueling device100 is engaged with the fuel receptacle 22 of the receiver aircraft 20(in some cases this process can continue until the refueling processends), the maneuvering instructions module 1820 can be configured toreturn to block 2005 and re-determine the receiver aircraft's 20 spatialdisposition with respect to the engagement area related thereto.

In some examples, in case the receiver aircraft 20 is not positionedwithin the engagement area, maneuvering instructions module 1820 can beconfigured to calculate maneuvering instructions for positioning thereceiver aircraft 20 within the engagement area (block 2020). It can beappreciated that once the maneuvering instructions module 1820determines the receiver aircraft's 20 spatial disposition with respectto the engagement area related thereto, it can also calculatemaneuvering instructions for positioning the receiver aircraft 20 withinthe engagement area related thereto. Maneuvering instructions module1820 can also provide the calculated maneuvering instructions forpositioning the receiver aircraft 20 (and, in some cases, an auto pilotsystem that controls the maneuvering of the receiver aircraft 20) withinthe engagement area related thereto to the pilot of the receiveraircraft 20 (block 2030) and return to block 2005.

It is to be noted that, in some cases, as indicated herein, maneuveringinstructions module 1820 can be configured to provide the maneuveringinstructions by using a light directing system. Such light directingsystem can be mounted, for example, on the tanker aircraft 12, at anylocation visible to the receiver aircraft 20 pilot. In some cases, thelight directing system can provide the pilot of the receiver aircraft 20with maneuvering instructions on three axes: forward-backward,left-right and up-down, thus enabling it to maneuver the receiveraircraft 20 to the engagement area 2110. Alternatively or additionally,the maneuvering instructions can be provided by using voice commands(e.g. by utilizing speakers, pilot headset, etc.) or by any other meansknown per se. In some cases, maneuvering instructions module 1820 can beconfigured to communicate the maneuvering instructions to an auto pilotsystem of the receiver aircraft 20, if such system exists.

It is to be noted that, with reference to FIG. 20, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also be noted that whilst the flow diagrams are describedalso with reference to the system elements that realizes them, this isby no means binding, and the blocks can be performed by elements otherthan those described herein.

It is to be further noted that in some cases instead of monitoring thatthe receiver aircraft 20 is positioned within the engagement area, analternative light directing system can be used. Such an alternativelighting system can be designed to display alternative light indicationsdepending on the angle from which it is viewed. Thus, in some cases,viewing the light directing system from its bottom side can result indisplay of light in a certain color, looking at the same light directingsystem from its upper side can result in display of light in a secondcolor, looking at the same light directing system from its right sidecan result in display of light in a third color, and looking at the samelight directing system from its left side can result in display of lightin a fourth color. Additional angles can result in display of additionalcolors. When using such a light directing system, upon arrival of thereceiver aircraft 20 to the engagement area, the light directing systemcan be automatically directed to the receiver aircraft 20 (based on itscurrent determined spatial disposition) and provide a color indicationindicating that it is positioned within the engagement area. If thereceiver aircraft 20 does not maintain its position, the pilot willreceive appropriate color indications from the light directing system sothat he will be able to make the required corrections to maintain thereceiver aircraft's 20 spatial disposition.

Turning to FIG. 21, there is shown a flowchart illustrating a sequenceof operations carried out for providing steering commands to a refuelingdevice for maneuvering to an engagement enabling position, according tocertain examples of the presently disclosed subject matter. Steeringcontrol module 1830 can be configured to determine (it is to be notedthat in some cases, as indicated herein, such determination is made, forexample, repeatedly) the refueling device's 100 spatial disposition withrespect to the engagement enabling position (in which the boom member130 is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20) relatedthereto (block 2105), as further detailed with respect to FIG. 23.

Following determination of the refueling device's 100 spatialdisposition with respect to the engagement enabling position relatedthereto, steering control module 1830 can be configured to check if therefueling device 100 is positioned within the engagement enablingposition (block 2110). In case the refueling device 100 is positionedwithin the engagement enabling position (in which the boom member 130 isin a predetermined maximal spaced and spatial relationship with respectto the fuel receptacle 22 of the receiver aircraft 20), and at leastuntil the refueling device 100 is engaged with the fuel receptacle 22 ofthe receiver aircraft 20 (in some cases this process can continue untilthe refueling process ends), the steering control module 1830 can beconfigured to return to block 2105 and re-determine the refuelingdevice's 100 spatial disposition with respect to the engagement enablingposition related thereto.

In case the refueling device 100 is not positioned within the engagementenabling position (in which the boom member 130 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20), steering control module 1830can be configured to calculate steering commands for maneuvering therefueling device 100 to an engagement enabling position, in which theboom member 130 is in a predetermined maximal spaced and spatialrelationship with respect to the fuel receptacle 22 of the receiveraircraft 20 (block 2120). It can be appreciated that once the steeringcontrol module 1830 determines the refueling device's 100 spatialdisposition with respect to an engagement enabling position relatedthereto, it can also calculate steering commands for maneuvering therefueling device 100 to an engagement enabling position related thereto.Steering control module 1830 can also provide the refueling device 100with calculated steering commands for maneuvering the refueling device100 to an engagement enabling position related thereto (block 2130) andreturn to block 2105. The steering commands can control the operation ofcomponents of the spatial control system 160 and/or the force generatingarrangement 190.

It is to be noted that, with reference to FIG. 21, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should also be noted that whilst the flow diagrams are described alsowith reference to the system elements that realizes them, this is by nomeans binding, and the blocks can be performed by elements other thanthose described herein.

Turning to FIG. 22, there is provided a flowchart illustrating asequence of operations carried out for determining the receiveraircraft's spatial disposition with respect to the engagement arearelated thereto, according to certain examples of the presentlydisclosed subject matter. In some cases, maneuvering instructions module1820 can be configured to acquire an image of the receiver aircraft 20(block 2210).

For that purpose, in some cases, maneuvering instructions module 1820can be configured to utilize sensor control module 1810 for repeatedly(e.g. every pre-determined period) or continuously (e.g. in the form ofa video stream) acquiring an image of the area aft the refueling device100 and/or aft the tanker aircraft 12, at a predetermined Field of View.Such Field of View can depend, inter alia, on the distance from which areceiver aircraft 20 is to be identified. In some cases, the farther itis required to identify the receiver aircraft, the larger the Field ofView is.

It is to be noted that although reference in the description issometimes made to an image, any other data that can be indicative ofpresence of a receiver aircraft can be utilized mutatis mutandis (e.g.radar data, acoustic signature data, etc.).

For the purpose of acquiring an image, sensor control module 1810 can beconfigured to utilize sensor 1890. In some cases, one or more sensor/s1890 can be mounted on the refueling device 100 and/or on the tankeraircraft 12. As indicated herein, in some cases the imaging system 150can be used as one or more of the sensor/s 1890. It is to be noted that,as indicated herein, the imaging system 150 can, in some cases, compriseone or more FLADAR units.

It can be appreciated that for acquiring an image of the receiveraircraft 100, the receiver aircraft 100 should be present in the sensedarea (e.g. the sensing volume 159). In some cases the receiver aircraft20 is expected to approach the refueling device 100 and/or the fueltanker 12 for the refueling process to begin. In some cases, theapproach of receiver aircraft 20 to the refueling device 100 is madefrom a certain direction or through a virtual funnel such as, forexample, from the rear and bottom side of the refueling device 100and/or the fuel tanker 12 while the pilot of the receiver aircraft 20has a line of sight to the refueling device 100 and/or the fuel tanker12. However, in other cases, other directions of approach are alsopossible (e.g. approach from the front and bottom side of the refuelingdevice 100 and/or the fuel tanker 12, etc.), depending, inter alia, onthe characteristics of the receiver aircraft 20 (e.g. the location ofthe fuel receptacle 22 of the receiver aircraft 20, etc.).

In some cases, maneuvering instructions module 1820 can be configured toanalyze sensed images in order to determine if a receiver aircraft 20can be identified within the sensed image. It is to be noted that suchanalysis can be performed using various known methods and techniques,such as, in the case of digital images, image correlation, etc.

In some cases, maneuvering instructions module 1820 can be configured tocause the signaling system to provide the pilot of the receiver aircraft20 with a notification indicating that its location with respect to theengagement area has been acquired. Such indication can be provided, forexample, by a signaling system (e.g. a lighting system mounted on therefueling device 100 and/or on the tanker aircraft 12, etc.).Additionally or alternatively, the indication can be a voice indicationprovided to the pilot of the receiver aircraft 20 (e.g. by utilizingspeakers, pilot headset, etc.). Additionally or alternatively, theindication can be any other indication (including visual or voiceindication) provided to the pilot of the receiver aircraft 20 (e.g. byutilizing speakers, pilot headset, a display, a light, etc.).

In some cases, maneuvering instructions module 1820 can be furtherconfigured to fetch configuration data (block 2220), including, interalia, data indicative of the engagement area specification. As detailedherein, the engagement area can be defined by various specificationsthat depend on several parameters, such as, for example, the length ofthe hose 52, the flight speed, the flight altitude, weather conditions,the fuel pressure within the hose 52, the location of the fuelreceptacle 22 of the receiver aircraft 20, etc.

In some cases, maneuvering instructions module 1820 can be furtherconfigured to fetch a reference image of a reference receiver aircraft(block 2230). In some cases the reference image is fetched inter aliaaccording to the fetched configuration data and/or the type of thereceiver aircraft 20 (e.g. F-15, F-16, etc.). Such a reference image canbe an image of an aircraft similar to the actual receiver aircraft 20,and in some cases of identical type as the actual receiver aircraft 20.If necessary, the maneuvering instructions module 1820 can obtaincurrent measurements for certain parameters in the configuration DR1860, to compute appropriate engagement area specifications.

It is to be noted that such a reference image should depict a scene inwhich the reference aircraft is positioned within the engagement areahaving the fetched specification (fetched in block 2220). In some cases,the reference image can depict a scene in which the reference aircraftis not positioned within the engagement area having the fetchedspecification, however the offset of the reference receiver aircraftfrom the engagement area can be calculated or alternatively is a-prioriknown.

Maneuvering instructions module 1820 can be further configured toutilize the reference image of a reference receiver aircraft within theengagement area having the fetched specification (or not within suchengagement area but with data of its offset from the engagement area)for calculating the relative spatial disposition of the receiveraircraft with respect to the engagement area (block 2240), for exampleusing methods and techniques known per se (such as, in the case ofdigital images, image correlation, etc.).

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the receiver aircraft 20 withrespect to the engagement area, an appropriate 3-D model can be selected(for example according to the type of the receiver aircraft 20) and the3-D model can be adapted using current measurements (e.g. obtained bythe sensor 1890) and respective parameters of the 3-D model.

It is to be noted that various other methods and techniques can be usedin order to determine the receiver aircraft's 20 spatial dispositionwith respect to the engagement area.

It is to be noted that, with reference to FIG. 22, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also be noted that whilst the flow diagrams are describedalso with reference to the system elements that realizes them, this isby no means binding, and the blocks can be performed by elements otherthan those described herein.

Turning to FIG. 23 there is provided a flowchart illustrating a sequenceof operations carried out for determining the refueling device's 100spatial disposition with respect to the engagement enabling position,according to certain examples of the presently disclosed subject matter.In some cases, steering control module 1830 can be configured to acquirean image of the receiver aircraft 20 (block 2310), and, in some cases,more specifically, of the area of the fuel receptacle 22 of the receiveraircraft 20.

For that purpose, in some cases, steering control module 1830 can beconfigured to utilize sensor control module 1810 for repeatedly (e.g.every pre-determined period) or continuously acquiring an image (it isto be noted again that although reference in the description is made toan image, any other data that can be indicative of presence of areceiver aircraft can be utilized mutatis mutandis) of the area aft therefueling device 100, at a predetermined Field of View. Such Field ofView can depend, inter alia, on the distance from which a receiveraircraft 20, and more specifically a fuel receptacle 22 thereof, is tobe identified. In some cases, the farther it is required to identify thereceiver aircraft, and more specifically a fuel receptacle 22 thereof,the larger the Field of View is.

For the purpose of acquiring an image, sensor control module 1810 can beconfigured to utilize sensor 1890. In some cases, one or more sensor/s1890 can be mounted on the refueling device 100 and/or on the tankeraircraft 12. As indicated herein, in some cases the imaging system 150can be used as one or more of the sensor/s 1890.

It can be appreciated that for acquiring an image of the receiveraircraft 100, and more specifically a fuel receptacle 22 thereof, thereceiver aircraft 100, and more specifically a fuel receptacle 22thereof, must be present in the sensed area (e.g. the sensing volume159). In some cases, the receiver aircraft 20 is expected to bepositioned within the engagement area related thereto.

In some cases steering control module 1830 can be configured to analyzea sensed image in order to determine if a receiver aircraft 20, and morespecifically a fuel receptacle 22 thereof, can be identified within thesensed image. A series of images can be analyzed, each substantiallyimmediately after it has been captured (for example as describedherein), in order for the steering control module 1830 to be able toprovide steering commands that are based on the actual (dynamic)relative position of the refueling device 100 and the engagementenabling position.

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the refueling device 100 withrespect to the engagement enabling position, an appropriate 3-D modelcan be selected (for example according to the type of the receiveraircraft 20) and the 3-D model can be adapted using current measurements(e.g. obtained by the sensor/s 1890) and respective parameters of the3-D model.

It is to be noted that such analysis can be performed using variousknown methods and techniques, such as, in the case of digital images,image correlation, etc.

In some cases, steering control module 1830 can be further configured tofetch configuration data (block 2320), including, inter alia, dataindicative of the engagement enabling position specification. Asdetailed herein, the engagement enabling position can be defined by apredetermined maximal spaced and spatial relationship with respect tothe fuel receptacle 22 of the receiver aircraft 20. As further indicatedherein, such configuration data can depend on several parameters, suchas, for example, the length of the hose 52, the flight speed, the flightaltitude, weather conditions, the fuel pressure within the hose 52, thelocation of the fuel receptacle 22 of the receiver aircraft 20, etc. Theconfiguration data is fetched according to current measurements andrespective parameters stored in association with each set ofconfiguration data.

In some cases, steering control module 1830 can be further configured tofetch a reference image of a reference receiver aircraft, and morespecifically a fuel receptacle thereof (block 2330). In some cases thereference image is fetched inter alia according to the fetchedconfiguration data (which, in turn, was fetched according to currentmeasurements and respective parameters stored in association with eachset of configuration data). Such a reference image can be an image of anaircraft, and more specifically a fuel receptacle thereof, similar, andin some cases identical to, the actual receiver aircraft 20, and morespecifically, an actual fuel receptacle 22 of the actual receiveraircraft 20.

It is to be noted that such a reference image should depict a scene inwhich the reference aircraft, and more specifically a fuel receptaclethereof, is positioned within an engagement enabling position having thefetched specification (fetched in block 2320). In some cases, thereference image can depict a scene in which the reference aircraft, andmore specifically a fuel receptacle thereof, is not positioned withinthe engagement enabling position having the fetched specification,however the offset of the reference receiver aircraft from theengagement enabling position can be calculated or alternatively isa-priori known.

In some cases, steering control module 1830 can be further configured toutilize the reference image of a reference receiver aircraft, and morespecifically a fuel receptacle thereof, within the engagement areahaving the fetched specification (or not within such engagement area butwith data of its offset from the engagement area) for calculating therelative spatial disposition of the receiver aircraft 20, and morespecifically the fuel receptacle 22 thereof, with respect to anengagement enabling position (block 2340), for example using methods andtechniques known per se (such as, in the case of digital images, imagecorrelation, etc.).

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the refueling device 100 withrespect to engagement enabling position, an appropriate 3-D model can beselected (for example according to the type of the receiver aircraft 20)and the 3-D model can be adapted using current measurements (e.g.obtained by the sensor 1890) and respective parameters of the 3-D model.

It is to be noted that, with reference to FIG. 23, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also be noted that whilst the flow diagrams are describedalso with reference to the system elements that realizes them, this isby no means binding, and the blocks can be performed by elements otherthan those described herein.

Looking, by way of example, at FIG. 28, there is shown an illustrationof an example of a sensed image indicating that the refueling device isnot positioned in an engagement enabling position, according to certainexamples of the presently disclosed subject matter. In some cases, thesensed image of the receiver aircraft 20, and more specifically a fuelreceptacle 22 thereof, and the reference image of the reference receiveraircraft, and more specifically a fuel receptacle thereof, can containsome elements (e.g. 2810, 2820, 2830, 2840, etc.) that enabledetermination of the sensed image offset from the reference image(thereby enabling determination of the offset of the refueling device100 from an engagement enabling position, in which the boom member 130is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20). It is tobe noted that virtual cross 2850 indicates the center of the image. Suchelements (e.g. 2810, 2820, 2830, 2840) can be used, for example byvarious known per se image correlation algorithms in order to determinethe spatial disposition of the receiver aircraft 20, and morespecifically the fuel receptacle 22 thereof, with respect to anengagement enabling position. The illustration of FIG. 28 is providedfor clarity of explanation only and is by no means binding.

Attention is now drawn to FIG. 29, showing an illustration of an exampleof a reference image indicating that the refueling device is positionedin an engagement enabling position, according to certain examples of thepresently disclosed subject matter. Looking at the illustration, it canbe appreciated that the fuel receptacle of a receiver aircraft should bealigned with the cross 2850 (that indicates the center of the image) andthat elements 2810, 2820, 2830, and 2840 should also be aligned with thecross 2850 vertical and horizontal axis, thus indicating that arefueling device is positioned in an engagement enabling position, inwhich the boom member 130 is in a predetermined maximal spaced andspatial relationship with respect to the fuel receptacle 22 of thereceiver aircraft 20. It can be appreciated that there is an offsetbetween the sensed image shown in FIG. 28 and the reference image shownin FIG. 29, thus indicating that at the time the sensed image shown inFIG. 28 was sensed, the refueling device 100 was not in an engagementenabling position. The illustration of FIG. 29 is provided for clarityof explanation only and is by no means binding.

It has been indicated herein that the engagement enabling position is aposition from which utilization of the force generating arrangement 190enables the nozzle 135 to engage with the fuel receptacle 22 of thereceiver aircraft 20. Therefore, in some cases, there can be more thanone engagement enabling position that meets such criteria and thus, insome cases, a certain offset between the sensed image and the referenceimage can be allowed, as long as the refueling device is in a positionfrom which utilization of the force generating arrangement 190 enablesthe nozzle 135 to engage with the fuel receptacle 22 of the receiveraircraft 20.

It is to be noted that various other methods and techniques can be usedin order to determine the receiver aircraft's 20 spatial dispositionwith respect to the engagement enabling position, including the knownper se 3-D modeling adaptation and/or the selection of the referenceimage which provides the highest correlation to the sensed data.

Operation Mode II

In this operation mode, once the tanker aircraft 12 and receiveraircraft 20 are in close proximity and flying in formation, with thereceiver aircraft 20 at a position behind the tanker aircraft 12, therefueling device is flown into engagement with the fuel receptacle 22 ofthe receiver aircraft 20 by an operator.

In a first example of Operation Mode II, the operator is stationed inthe tanker aircraft 12, which comprises a suitable control stationoperatively connected to the refueling device, which can be refuelingdevice 100 according to the first example or alternative variationsthereof, or refueling device 200 according to the second example oralternative variations thereof, or a refueling device according to othersuitable examples thereof according to the first aspect of the presentlydisclosed subject matter. The control station comprises a display devicefor suitably displaying data relating to the spatial disposition of therefueling device at least with respect to the receiver aircraft 20 andthe fuel receptacle 22 thereof, and an output device for providingcontrol signals to the refueling device for controlling the flightthereof.

For example, and referring to refueling device 100 according to thefirst example or alternative variations thereof, the display device cancomprise a screen display that displays real time images (2D, and/orstereoscopic images, and/or 3D images), for example in video streams,provided by the imaging system 150. Additionally or alternatively, suchimaging can be provided or augmented via suitable cameras or otherimaging units, provided on the tanker aircraft 12 and/or the receiveraircraft 20 and/or any other suitable air vehicle in the vicinity of therefueling device 100, and thus in at least some such examples therefueling device 100 can omit the imaging system 150.

The output device can comprise, for example, a joystick that ishand-manipulated by the operator to provide the required control signalsto the spatial control system 160, in particular the controllableaerodynamic surfaces thereof, to provide the required design angleθ_(des) between the boom axis 131 and the forward direction A, whileflying the refueling device 100 into proximity with the receiveraircraft 20 and the fuel receptacle 22 thereof.

The operator first ensures that the refueling device 100 is being towedbehind the tanker aircraft 12 at a suitable distance therefrom, and cancontrol this spacing by extending or retracting the hose 52 with respectto the tanker aircraft 12.

When the operator determines that the nozzle 135 is properly alignedwith the fuel receptacle 22 (the boom member 130 and boom axis 131 beingat the design angle θ_(des) to the forward direction A) and sufficientlyclose thereto, i.e., at the engagement enabling position at apredetermined spacing from the receiver aircraft, said boom axis beingaligned in an engagement enabling orientation at said spaced position,the operator provides a suitable control signal to the refueling device100 to activate the force generating arrangement 190, i.e., by deployingthe air brakes 195, 196, generating a force along boom axis 131 thateffectively pushes the nozzle into engagement with the receptacle 22. Inother words, once the refueling device 100 is at the aforesaidengagement enabling orientation and spaced position, the boom member issubsequently moved along said boom axis towards the receiver aircraftfor enabling fuel communication therebetween. Movement of the boommember can be effected in one of two ways, or combination thereof: therefueling device 100 remains in the spaced position, and the boom member130 is extended telescopically; the boom member 130 can be in theretracted or extended position, and the refueling device 100 is bodilymoved towards the receiver aircraft for enabling fuel communicationtherebetween.

Thereafter, the air brakes 195, 196 are retracted, and fuel is pumped tothe receiver aircraft 20 from the tanker aircraft 12. The refuelingdevice 100 can be automatically or manually controlled to maintain therequired design angle θ_(des) between then boom axis 131 and the forwarddirection A during refueling.

Once refueling is completed, the operator disengages the nozzle 135 fromthe fuel receptacle 22 and flies the refueling device 100 at least to asafe position away from the receiver aircraft 20, and/or the receiveraircraft 20 maneuvers to such a position, and the refueling device 100can be retracted back into the tanker aircraft 12, or reused withanother receiver aircraft 20.

It is to be noted that the same operator can early out Operation Mode IIwith each of the plurality of refueling systems 50 of the tankeraircraft 12. Alternatively, the tanker aircraft 12 can comprise adedicated control station operatively connected to each refueling device100, and operated by a respective dedicated operator; thus differentoperators control each of the refueling devices 100.

In an alternative variation of this example of Operation Mode II, theoperator is stationed in another aircraft different from the receiveraircraft 20 or tanker aircraft 12, or is located in a ground station,and Operation Mode II can be carried out in a similar; manner to thatdescribed above for the first example, mutatis mutandis, with the maindifference that the operator receives the data relating to the spatialdisposition of the refueling device at least with respect to thereceiver aircraft 20 and the fuel receptacle 22 thereof, and providescontrol signals to the refueling device for controlling the flightthereof, via a suitable communications link respect to the refuelingdevice 100, which is correspondingly equipped with suitablecommunication system.

In another alternative variation of this example of Operation Mode II,the operator is stationed in the receiver aircraft 20 rather than intanker aircraft 12, and Operation Mode II can be carried out in asimilar; manner to that described above for the first example, mutatismutandis, with the main difference that the operator receives the datarelating to the spatial disposition of the refueling device at leastwith respect to the receiver aircraft 20 and the fuel receptacle 22thereof, and provides control signals to the refueling device forcontrolling the flight thereof, via a suitable communications link withrespect to the refueling device 100, and the receiver aircraft 20 andthe refueling device 100 are each correspondingly equipped with asuitable communication system. Alternatively, in at least somecircumstances, the operator can have the refueling device 100 inparticular the boom member 130 and nozzle 135, and the fuel receptacle22 in the operator's visual field of view, and does not require theaforesaid spatial disposition data in order to control the refuelingdevice 100, and thus in such cases the refueling device 100 can omit theimaging system 150.

Clearly, Operation Mode II can be applied to other variations of thefirst example of refueling device 100, or to the second example ofrefueling device 200 or alternative variations thereof, in a similarmanner to that described above for the first example of refueling device100, mutatis mutandis.

It is to be noted that according to Operation Mode I and/or OperationMode H, the refueling unit can be selectively controlled to adopt analigned configuration with the hose 52. By way of non-limiting example,such a situation is illustrated in FIG. 2 for the fuselage-mountedsystem 50. Such a configuration can include controlling the spatialcontrol system 160 to align the longitudinal axis 111 with the forwarddirection A in the case of the first example of refueling device 100 oralternative variations thereof, or maintaining the boom 230 in aretracted configuration accommodated in body 210 in the case of thesecond example of refueling device 200 or alternative variationsthereof, for example.

Operation Mode III

In this operation mode, the tanker aircraft 12 and receiver aircraft 20are maneuvered to be in close proximity and flying in formation, withthe receiver aircraft 20 at a position behind the tanker aircraft 12. Itis first ensured that the refueling device 100 is being towed behind thetanker aircraft 12 at a suitable distance therefrom, and an operator(typically in the tanker aircraft) can control this spacing by extendingor retracting the hose 52 with respect to the tanker aircraft 12.

In a first example of Operation Mode III, the refueling device 100 isnot flown or controlled per se, but attains a stable configuration withthe boom member 135 at the required angle with respect to the forwarddirection A, design angle θ_(des). Accordingly the refueling device 100can optionally omit the controllable spatial control system 160, andinstead comprises a suitable configuration that provides stability tothe boom member 135 at this spatial disposition.

The receiver aircraft 20 maneuvers to a position where it can engage thenozzle to the receiver aircraft fuel receptacle, and when an operator inthe receiver aircraft (for example the pilot) determines that the nozzle135 is properly aligned with the fuel receptacle 22 and sufficientlyclose thereto, the operator provides a suitable control signal to therefueling device 100 to activate the force generating arrangement 190,i.e., by deploying the air brakes 195, 196, generating a force alongboom axis 131 that effectively pushes the nozzle into engagement withthe receptacle 22. Thereafter, the air brakes 195, 196 are retracted,fuel is pumped to the receiver aircraft 20 from the tanker aircraft 12,and the refueling device 100 maintains the required design angle θ_(des)between then boom axis 131 and the forward direction A during refueling.

The receiver aircraft can comprise a display device for suitablydisplaying data relating to the spatial disposition of the refuelingdevice at least with respect to the receiver aircraft 20 and the fuelreceptacle 22 thereof.

For example, and referring to refueling device 100 according to thefirst example or alternative variations thereof, the display device cancomprise a screen display that displays to the operator (for example thepilot or navigator of the receiver aircraft) real time images (2D,and/or stereoscopic images, and/or 3D images), for example in videostreams, provided by the imaging system 150. Additionally oralternatively, such imaging can be provided or augmented via suitablecameras or other imaging units, provided on the tanker aircraft 12and/or the receiver aircraft 20 and/or any other suitable air vehicle inthe vicinity of the refueling device 100, and thus in at least some suchexamples the refueling device 100 can omit the imaging system 150.

Alternatively, in at least some circumstances, the operator can have therefueling device 100 in particular the boom member 130 and nozzle 135,and the fuel receptacle 22 in the operator's visual field of view, anddoes not require the aforesaid spatial disposition data, and thus insuch examples the refueling device 100 can omit the imaging system 150.

In at least some circumstances, the operator/pilot can maneuver thereceiver aircraft 12 such as to provide a suitable force via the fuelreceptacle 22 to engage the nozzle 135 thereto, or alternatively thereceiver aircraft can comprise a suitable arrangement configured forengage the nozzle 135 to the fuel receptacle 22 without the need togenerate such a force, and thus in such examples the refueling device100 can omit the force generating arrangement 190.

Once refueling is completed, the operator disengages the nozzle 135 fromthe fuel receptacle 22 and the receiver aircraft 20 maneuvers to atleast a safe position spaced from the refueling devoice 100, and therefueling device 100 can be retracted back into the tanker aircraft 12,or reused with another receiver aircraft 20.

It is to be noted that Operation Mode III can be carried out with eachof the plurality of refueling systems 50 of the tanker aircraft 12.

Clearly, Operation Mode III can be applied to other variations of thefirst example of refueling device 100, or to the second example ofrefueling device 200 or alternative variations thereof in a similarmanner to that described above for the first example of refueling device100, mutatis mutandis.

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

It should be noted that the word “comprising” as used throughout theappended claims is to be interpreted to mean “including but not limitedto”.

While there has been shown and disclosed examples in accordance with thepresently disclosed subject matter, it will be appreciated that manychanges may be made therein without departing from the spirit of thepresently disclosed subject matter.

It is to be understood that the presently disclosed subject matter isnot limited in its application to the details set forth in thedescription contained herein or illustrated in the drawings. Thepresently disclosed subject matter is capable of other embodiments andof being practiced and carried out in various ways. Hence, it is to beunderstood that the phraseology and terminology employed herein are forthe purpose of description and should not be regarded as limiting. Assuch, those skilled in the art will appreciate that the conception uponwhich this disclosure is based may readily be utilized as a basis fordesigning other structures, methods, and systems for carrying out theseveral purposes of the present presently disclosed subject matter.

It will also be understood that the system according to the presentlydisclosed subject matter may be a suitably programmed computer.Likewise, the presently disclosed subject matter contemplates a computerprogram being readable by a computer for executing the method of thepresently disclosed subject matter. The presently disclosed subjectmatter further contemplates a machine-readable memory tangibly embodyinga program of instructions executable by the machine for executing themethod of the presently disclosed subject matter.

The invention claimed is:
 1. A refueling device for use in in-flightrefueling operation, comprising: (a) a body having a longitudinal axisand configured for being towed by a tanker aircraft via a fuel hose atleast during in-flight refueling operation, and comprising a boom memberhaving a boom axis and configured to enable fuel to be transferred fromsaid fuel hose to a receiver aircraft along said boom axis during saidin-flight refueling operation; (b) spatial control system configured forselectively ensuring maintaining a desired non-zero angular dispositionbetween said boom axis and a forward direction at least during in-flightrefueling, wherein at least during said in-flight refueling the boomaxis is at a non-zero angular displacement with respect to thelongitudinal axis of the body.
 2. The refueling device according toclaim 1, the boom member comprising a fuel delivery nozzle, and thereceiver aircraft comprising a fuel receptacle configured for engagingwith the fuel delivery nozzle to enable refueling of the receiveraircraft.
 3. The refueling device according to claim 1, wherein saidangular disposition is defined about at least one of a pitch axis, a yawaxis and a roll axis of said refueling device.
 4. The refueling deviceaccording to claim 1, wherein said angular disposition is such as toensure that the boom axis is at a predetermined design angle withrespect to the receiver aircraft.
 5. The refueling device according toclaim 1, wherein said design angle is about 30°.
 6. The refueling deviceaccording to claim 1, wherein said refueling device is configured formaintaining said desired non-zero angular disposition between said boomaxis and said forward direction at least prior to engagement of saidfuel delivery nozzle with a fuel receptacle of a receiver aircraft thatis flying in formation aft of the tanker aircraft.
 7. The refuelingdevice according to claim 1, wherein said spatial control system isfurther configured for selectively providing control moments in at leastone of pitch, yaw and roll wherein to enable the refueling device to beflown while towed by the tanker aircraft in said forward direction viasaid fuel hose.
 8. The refueling device according to claim 1, whereinsaid spatial control system comprises selectively controllableaerodynamic control system.
 9. The refueling device according to claim8, wherein said selectively controllable aerodynamic control systemcomprises a forward set of aerodynamic control surfaces mounted to saidbody, and an aft set of aerodynamic control surfaces mounted to saidbody in longitudinally aft spaced relationship with respect to saidforward set of aerodynamic control surfaces.
 10. The refueling deviceaccording to claim 9, wherein said aft set of aerodynamic controlsurfaces comprises at least two said control surfaces mounted to saidbody in Vee configuration.
 11. The refueling device according to claim1, wherein the boom member is pivotably mounted to the body about apivot axis.
 12. The refueling device according to claim 1, wherein theboom member is pivotable between a stowed position and a deployedposition, wherein in the stowed position the boom member is accommodatedin the body, and wherein in the deployed position the boom member ispivoted away from the body about said pivot axis to provide saidnon-zero angular displacement between the boom axis and the longitudinalaxis of the body.
 13. The refueling device according to claim 1, whereinsaid non-zero angular displacement between the boom axis and thelongitudinal axis of the body is between 5° and 85°.
 14. The refuelingdevice according to claim 1, wherein said non-zero angular displacementbetween the boom axis and the longitudinal axis of the body is between15° and 70°.
 15. The refueling device according to claim 1, wherein saidnon-zero angular displacement between the boom axis and the longitudinalaxis of the body is between 25° and 40°.
 16. The refueling deviceaccording to claim 1, wherein said boom member is selectively reversiblytelescopically deployable along said boom axis at least during saidin-flight refueling.